ULTRAVIOLET STERILIZATION (How UV-C Sterilizers Work).
The MOST IN-DEPTH article about the Benefits & Myths about Aquarium/Pond UV Sterilization, Clarification; Written with 34+ years of hands-on experience/research
UV Bulb Trouble Shooting Video
We HIGHLY SUGGEST anyone with a UV Sterilizer, thinking of purchasing a UV Sterilizer, needing to replace a UV Bulb, or having difficulties watch this video!!
A MUST WATCH!
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UV Germicidal Sterilizers.
As well as Efficient Compact, Internal, and Custom UV Sterilizers.
Here is What a Properly Installed, Well Designed UV Sterilizer (or Steriliser) Can Do for your POND or AQUARIUM:
• Clear Green Water in Aquariums or Ponds. Please see the picture to the left for a before and after picture of an aquarium with green water; As well as a comparison between a pond without UV Sterilization and one of our client's ponds with a UV Sterilizer/Clarifier (Click on the picture to enlarge)
• Kill most suspended bacteria and many viruses in the water column, while not affecting bacterial colonies in filter media and substrate
• Improve Redox Balance in aquarium or pond and thus improve the fish’ ability to fight disease (this has been proven in well researched human studies too)
• Aid in the control of parasites such as Ich or Cryptocaryon by improving immune function and at very low flows (under 8-12 gph per watt) can more directly aid in parasite control in the water column.
• Unfortunately many of the UV Sterilizers flooding the market for under $50 including "Hang on Back" (HOB) and many "In Tank" Submersible UVs at best can ONLY control algae and very limited bacterial blooms, these CANNOT perform the level one Sterilization needed for true disease control and aid to Redox Balance.
As well, these low end UVs often have very limited life times due to design.
By using low end equipment such as "Killing Machines" and then claiming these did nothing to protect the health of their fish is NOT a scientific argument against these devices. As well despite these observable and researched facts, many still will deny these benefits other than clarification.
This problem of denying facts while often making "straw man" attacks such as claiming articles like this are "based on selling this equipment" is still unfortunately still quite common, often in anecdotal, "cut & paste information" forums.
PLEASE READ THIS ENTIRE ARTICLE TO UNDERSTAND WHY!
UV Sterilization Overview
Ultraviolet radiation, referred to as UV or UVC radiation for sterilization purposes is a form of ionizing and non-ionizing radiation.
UV light energy is classified as such: UVA 400 nm - 320 nm, UVB 320 nm - 290 nm, and UVC 290 nm - 100 nm.
UVA and UVB that can reach the Earth’s surface are primarily non-ionizing and do not have enough energy to ionize atoms. However, the longer wave UVA and UVB can cause molecules to vibrate and rotate resulting in heating up.
The shorter wave UVC (used in UV Sterilization) light will ionize many atoms and molecules as compared to the even shorter wave Gamma Rays which will ionize most atoms.
Ultra violet sterilization is an effective tool for disease prevention in aquariums, ponds and for general water quality control such as Green Ponds or Cloudy Aquariums.
As well the use of UVC Sterilization is useful in home, office, hospital air purification & even UVC/Redox Blood therapy.
For this reason a properly installed & designedUV Sterilizer helps improves a fish’ chances in fighting bacterial diseases or even parasitic diseases such as Ich that UV Sterilization is less effective in destroying directly .
Part of the reason for UV Sterilization is that the UVC irradiation which is contained in the unit will break down oxidizers in the water column that would otherwise lower a fish’ immunity (Redox Balance), this aspect is often missed as many only focus on the germicidal/algaecidal properties of UV Sterilizers.
Please read this article for more about this subject: “Fish Immune System and UV Sterilization”.
As for the Redox Balance, this is an often overlooked aspect of both freshwater and saltwater aquarists. The Redox Balance is basically the oxidation and reduction properties of water (the oxidation side of Redox).
Most experts now agree that the Redox should be +300 to -100 mV for marine or +125 to -200 mV for freshwater for healthy fish immunity, which a UV Sterilizer can help maintain this balance. Reference (Copyright Carl Strohmeyer)
In fact a tidal wave of new research (mostly outside the aquatic community) is demonstrating just this aspect of UV Sterilization, including the use of UV-C to demonstrate water quality.
There is a lot of new evidence as to the benefits of UV sterilization for ALL fish, and many myths have been dispelled such as “UV Sterilizers destroying beneficial nitrifying bacteria”. I am also constantly researching this subject, so this article may not be the same article in three months, so please check back.
UV Sterilization is also effective for controlling suspended algae (green water) in ponds (along with proper filtration such as Veggie Filters/pressurize filters, please see this article: “A Clear Pond; pond information”)
UVs are also useful in Reef aquaria, especially new ones where the chance of disease introduction is high and the UVs help in keeping a balanced Redox Potential is useful. For those who prefer, the sterilizer can be placed on a timer or turned on and off as needed once the aquaria has aged.
One argument against UV Sterilizers in ponds is that they are not natural, but for the clarity most persons want out of their pond, this is not possible without either UV sterilization or many other pond configurations.
Many articles I have read state that a UV is not that beneficial to an established aquarium as a healthy aquarium depends on beneficial bacteria typically growing on media in your filter which neutralize ammonia. Unfortunately the problem with this statement is beneficial bacteria belongs in the filter, not in the open water.
Also the lack of a UV Sterilizer may be fine for some advanced aquarists who are not adding fish and have a healthy Redox Potential/Balance, but not in the real world of average and above average aquarists that I have dealt with in the 100s of aquariums I have serviced.
To be even more blunt, I conducted several controlled studies in the 1990’s (for which my ongoing research is to explain some of the results, such as improved immunity). In these studies where I mostly used goldfish (Orandas & Ryukins), the results were clear in that the incidence of disease was lower, longevity was longer, and over all vitality was better. The results were even better yet when improved feeding, improved cleaning, improved mineralization (positive mineral ions) are thrown into the equation.
Please read on for further understanding of functions, facts and myths, maintenance, & more in depth information as the article progresses!
BASIC FACTORS DETERMINING THE CORRECT UV STERILIZER:
• Flow rate
• Dwell time (related to flow rate)
• Water Turnover in pond or aquarium per hour
*As well the circulation pattern can affect UV Sterilization effectiveness
• Distance of UV Lamp from UV Sterilizer containment 'wall'
• Temperature of water
• Pre-Filtration including Turbidity of water
(A) Water Flow, Dwell/ Exposure Time; UV Sterilization Levels
This is easily the most important simple aspect of proper UV Sterilizer set up and all the gimmicks (like “twists” and “wipers”) will not help a poorly installed UV with high flow rates of water passing through the unit without proper exposure time at the correct distance from the UVC Lamp/Bulb.
In fact this is where most UV Sterilizers installed in ponds fall short as pond keepers will place (as an example) a 9 watt UV powered with a 1000 gph pump which is 2-4 times the effective flow rate for a pond installation (often as per very poor directions by the manufacturer).
This problem is also common among reef aquarists with high flow rate sump pumps attached to UV Sterilizers incompatible with the flow rate, resulting in the common and incorrect statement that "the UV Sterilizer was useless".
Admittedly flow rate is a generalization expressed to simplify mW/cm2 that is absorbed/transmitted to pathogens/algae (please read further in this article for more in depth explanation of UVC Penetration/mW/cm2).
I use this flow calculation as a simplified method as it has tested well over the years and PROVEN effective when other aspects of UV Sterilization are factored in. Obviously there are other factors such as distance from the UV Sterilizer wall, water turbidity, quartz sleeve cleanliness, UV bulb condition/age, and more (again that are explained in this article).
As well many UV manufacturers will over state their UV Sterilizer abilities as per maximum flow rates (although this does not necessarily make such a UV Sterilizer a poor/inferior product as some other web sites claim). I will state based on many years experience and experimentation that will the calculations provided here are THE MOST accurate, not exaggerated claims by many UV manufacturers.
Dwell/ Exposure Time is closely related to water flow, however with many of the compact UV Sterilizers and even more so pressurized pond or aquarium canister filters with UVs the difference IS important.
Put simply if you have a 9 Watt compact UVC Bulb with approximately 5 inches of lamp exposure versus an 8 watt HO Straight tube with approximately 11 inches; the 8 watt UVC Sterilizer is going to have a higher mW/cm2 even with one less watt of energy.
This is a very simple explanation, and there is more to this including sterilizer design, etc (which the article goes into further depth later), however this is a where a High Dwell/Exposure Time UV Sterilizer will beat any compact UV Sterilizer.
Please read this section for more on this important subject: DWELL TIME; A Controlled Experiment
(This is a MUST READ for any pond or aquarium keeper serious about UV Sterilization and/or Clarification!)
• The key to success is CORRECT water flow; including Contact Time (Dwell/Exposure Time), Cleanliness of the Bulb and/or Quartz Sleeve, water particulates, and water temperature.
Most UV Sterilizers are "Non-Directional", meaning the there is no specific inlet or outlet and water can flow either direction (the exception would be the Internal UV Pumps/Filters)
Please see the flow rate/turnover later in this article which further explains flow for Sterilization or clarification for aquariums, ponds or even pools.
Also note that the given flow rates are generalizations, with many Compact UV Sterilizers requiring the slower flow rate given over a Standard length UV (such as the TMC Pond Advantage/Vecton)
As well when ALL these Basic Factors are taken together (dwell, flow, distance, etc.), most internal/submersible, HOB UVs, Canister UVs fail at TRUE UV Sterilization (level 1 or 2) and these types of so-called UV Sterilizers in reality are at best UV Clarifiers!
*As a Clarifier; For Algae Control (Green Water and some Cloudy Water), 40-50 gph per watt is effective to maintain effective exposure for effective UVC sterilization/radiation (depending on model UV’s design).
High Efficiency (High Dwell/Exposure) UV Sterilizers such as the TMC Pond Advantage with long contact time as per the wattage and lamp can easily run as high as 50-60 gph per watt. The even higher efficiency (& dwell time) Pro Clear UV 30 can go 70+ gph per watt.
*As a Sterilizer; Generally for bacterial control (& many virus) a flow rate of 20-25 gph per watt (75-95 liters per hour, per watt), sometimes as high as 30-35 gph per watt for high efficiency UV Sterilizers such as the TMC Vecton UV.
*As a Sterilizer; For single cell parasite control (such as Cryptocaryon) as well as a few “stubborn” viruses, a flow under 10 gph (or even less) is necessary. This is often not 100% for all parasites of this type, so a UV Sterilizer should not be relied on as the sole preventative for these parasites!
Please see the section (“What Size UV Is Best”) further down in the article for more about flow rate. Admittedly this is a VERY basic and simplistic rule, with other factors such as flow design, interior wall gap from UV bulb, & even actual output of UVC per watt (Versus other wave lengths).
• The design of the unit should only allow a gap of .3 mm or less between the bulb or quartz sleeve and the wall of the unit for effective contact and temperature.
This is where Aquarium Canister UVs, 'Hang-On Back' UV Filters, Most Submersible/Internal UVs, and Pressurized Pond Filters (such as the Aquael, Nursery Pro, even the newer Via Aqua) fail miserably as there is too large a gap, and in general a poor flow design around the bulb/quartz sleeve (as well as flow rates far exceeding UVC bulb wattage capabilities)
• When figuring the flow (gph) of a water pump, consider the flow of water AFTER it passes through the UV clarifier and reaches the aquarium or top of water feature in a pond. For instance water pump or filter rated at 400 gph at 0 head pressure & 6 feet maximum head pressure (which is how all pumps are rated), will likely only push about 200 gph after being lifted 3 feet from a sump or up a water feature.
For a positive check of flow rate, simply use a stop watch (many cell phones have this feature), and place a container under the outlet. For example if one gallon is filled within 10 seconds, this is 6 gallons per minute or 360 gph. Many people are surprised how slow their pump actually is after applying head pressure.
Some pumps or filters lose head pressure more quickly than others (such as the Hagen Fluval), while other pumps are specifically designed to maintain higher head pressure over greater vertical distances (such as the Rio HF Series pumps).
See also this article about head pressure: Head Pressure in Aquarium and Pond Water Pumps
• Size of pipe/tubing on water flow:
Another consideration is the size of the PVC pipe or tubing coming from the pump. For instance a pump with a 1 inch outlet port that is rated at 2000 gph (for 0 head pressure) will likely not have an output of 2000 gph if the pipe/tubing used is ľ inch or less.
This same thought goes for the UV Sterilizer itself, in fact the Custom UV I have built only uses ˝ inch hose barbs so as to restrict the flow to under 350 gph which is the maximum effective rate.
It is also noteworthy that the flow rates I have already noted is not an exact rule, as reflection within the UV Sterilization chamber, the distance between bulb (or sleeve) and the walls of the unit, and the length of the bulb as per wattage of UVC output all affect this general guide (this is explained later in more depth).
The point as to bulb length is noteworthy, as I have found that increasing wattage with the same length bulb does NOT increase effectiveness proportionally to a given wattage. In fact a popular Pond UV that uses HO (High Output) UVC Bulbs (50 watt and 100 watt models) does not double the amount of water flow you can run through the unit even though it is double the wattage of comparable length UVC bulbs of half the wattage.
The TMC 110 Watt Pro Pond UV is much more effective than the popular HO UVs of 100 watts (each use two bulbs, the TMC uses two 55 watt of 36 inches while the “smart” HO UV uses two 50 watt bulbs of 18 inches), yet these HO UV Clarifiers cost much more which often leaves me scratching my head as to “why?” spend the money?
• Diverters/ By-pass Valves;
For pond UV applications (or high flow rate aquariums such as sump systems) it is usually best to have a ‘T’ with a ball valve to split the return line to the pond from the filter, this will allow the pond keeper to slow down the flow to the UV to the correct rate as per gph and wattage. (Please click on the picture to the left for an example of a UV diverter with a control valve and also to purchase them).
(B) Aquarium or Pond Water Turnover Rate:
It is important to have a flow rate that will turn over the pond or aquarium at least once every 2 to 3 hours for green algae control, once every 1 ˝-2 times per hour for disease prevention (Level One Sterilization), or up to 4 times per hour for stage 2 sterilization (I have achieved effective level one disease sterilization as tested with a bacterial cloud with as little as once per two hours with a good installation in an otherwise well maintained aquarium).
A turnover rate can also be less than accurate based on your method of plumbing; for instance if your water inlet and return are situated immediately adjacent to each other you will have areas of the aquarium or pond that are not well circulated.
Based on "house calls" I have made, adding additional power heads or other circulation devices do NOT make up for a poor flow pattern!!
The picture to the left shows the point I am making.
With sump use, many will simply place a UV Sterilizer in a loop circulating within the sump. This too results in re-cirulation of UVC irradiated water while most of the aquarium does not benefit from the use of the UV Sterilizer (with a sump the water needs to be returned directly to the aquarium after passing through the UV Sterilizer for maximum efficiency not connected with pick up and return from the sump).
Also many connect their Aquarium UVs to high flow sump pump that provides a flow rate well above level one sterilization.
Make sure to either use a diverter valve or simply use a second lower flow rate pump to attach your UV Sterilizer in-line from your sump back to your aquarium.
Please click on the picture to enlarge
In ponds, again I want to emphasize that many manufacturers will make claims of certain UV Sterilizers/Clarifier per pond size; however the flow rate through the UV and turnover rate is more important. As well many will correctly install a UV Sterilizer for their pond, ignoring the importance of good filtration combined with UV Sterilization. A correctly installed UV Clarifier often will not over come poor filtration and circulation.
Often this seeming contradiction of low flow rate versus higher turn over rate confuses some persons, but it is logical when one thinks about it, hopefully the table below or the more in depth sections further in this article will shed more light on this important aspect of correct UV Sterilization.
Flow Rate & Turnover Rate Table:
This table assumes:
(1) Low water turbidity
(2) A water temperature between 20 C (68 F) and 40 C (104 F)
(3) A gap of .3 mm or less between the bulb or quartz sleeve and the wall of the unit
(4) A GOOD water flow pattern inside the aquarium or pond.
(5) A clean Quartz sleeve/lamp and a hot cathode low pressure UV bulb/lamp with less than 6 months continuous use
Otherwise, lower flow rates and higher turnover WILL be required
Flow Rate (generalized)
(Green water control; Aquarium/Pond) The most popular application for ponds
40-50 gph per watt
(50-60 gph High Exposure/Dwell UV or even 70+ gph with Super High Exposure Pro Clear UV30)
Once per 2-3 hours
Level One Sterilization (Bacteria, some Virus)
The most common & recommended aquarium application
20-30 gph per watt
(30-35 gph High Exposure/Dwell UV)
1.5 times per hour
Level Two Sterilization (Parasites, “Stubborn” Viruses; Recommended for Swimming Pools)
Under 8 gph per watt
(8-12 gph High Exposure/Dwell UV)
3 to 4 times per hour
As one can see, there is obviously some variance in the gph per watt, this is not meant to be vague, but to reflect the variance in UV Sterilizers themselves.
This is not a perfect formula since it does not factor in dwell time, temperature, and pre-filtration. However most formulas only factor in flow rate as per µW/cm2 which is less complete than this formula.
In my three decades of experience using and even building I have found the formula I espouse here to be the most reliable, especially when one attempts to factor in the somewhat more subjective variables.
However I do provide a test to determine dwell time that I have not found a way to merge into the above formula other than to subtract as much as 40% off the flow rate for the many UVs sold with poor dwell times.
As an example, lower end Compact Sterilizers such as the Jebo have poor dwell time (exposure time) per watt and thus will require the lower flow rates (in fact some poorly designed units may require even lower flow rates), while top notch straight tube UV Sterilizers such as the TMC Vecton and Advantage can achieve the same results with higher flow rates and thus will be at the high end of flow rate suggestion per type of UV irridation.
As you can also see, if level two sterilization is required (as is generally necessary for swimming pool use as well as most “high end” marine fish importers such as Quality Marine USA), the need for large UV-C Sterilizer may be necessary for these large volumes of water such as the TMC 440 Watt Industrial UV Sterilizer pictured to the left.
For a further explanation of the subject of gph & turnover rates as it pertains to the correct UV for your application, see the section “What Size UV Sterilizer is Best”, please read this section to help use the above number to determine the best fit UV for your application.
Or please read, “Is Too Large a UV Sterilizer a Problem?” for further information about flow rate including very low gph per watt and parasite control.
(C) Temperature/Quartz Sleeves
Generally UV Sterilizer Bulbs used in aquatics employ low pressure mercury lamps (39% efficiency) vs. the medium/ pressure mercury lamps that have a much lower effectiveness (10%).
This is important to note as low pressure lamps are sensitive to water temperature while medium pressure are not (the poor efficiency of medium pressure lamps which produce much of their light in spectrums useless for sterilization makes this only quality negligible). The operating temperature spectrum at which low pressure UVC is effective is between 20 C (68 F) and 40 C (104 F). The keyword is OPERATING temperature as in a reasonably well designed unit the water is usually in the unit long enough to be warmed several degrees which generally means that a water temperature over 20 C (68 F) will work fine. So if your flow or unit design (or both) is not allowing this temperature, your effectiveness will be minimal.
Quartz sleeves help keep up a higher temperature, however in my tests with the same wattage units, (with and without Quartz sleeves) I only found a 5 degree F difference inside the UV Sterilizer when I turned off the units and then checked temperature differences, so this is another one of those statements about UV Sterilizers that I will challenge.
Quartz glass is also used in some UV Sterilization applications to protect a UVC light that is suspended above the water from spray (assuming the quartz glass is kept clean of mineral buildup). As per the latest data I have; quartz is about 99% efficient as per UVC penetration, so it is the best product for this use, however polycarbonate plastic is about 90% efficient, so this could also be used. I do not recommend acrylic (about 60% efficient) or standard float glass (about 40% efficient).
Although useful in some applications, quartz sleeves don't always allow as good of contact with the water and are difficult to keep clean, so in my opinion the benefits can be a wash.
Which brings me to key #3, keeping the bulb or quartz sleeve clean?
First, you want to change the UV bulb every 6 months for disease prevention or once every year at the beginning of the growing season for green algae prevention. You want to clean the quartz sleeve at this time too (using acetone). With a simple model without a quartz sleeve, you just throw away the dirty bulb.
Be careful of the latest gimmick in UV Sterilizers and that is wipers (great in theory though but NOT practical application), for more about these, please read this blog post: "UV Sterilizer Truths". I would also be aware of many other sources of inaccuracies in UV Sterilization, please read this blog which has regular posts dealing with these subjects: UV Sterilizer Blog
Back to temperature; if your water is very cold (such as a pond or even well water treatment system), I would suggest pre-heating your water before it passes through your UV Sterilizer unit, this is more effective than a quartz sleeve.
For further information about UV bulbs (lamps) and how they work, please see this article:
UV (UVC) Lamps (Bulbs) used in Aquariums and Ponds and how they work.
Aquarium Temperature with UV Sterilizer Use:
The section above deals temperatures inside the UV Sterilizer itself, not an aquarium, Please do not confuse the two as although the temperature inside the aquarium (& more likely a pond during cooler months) affects the effectiveness of the UV Sterilizer, the UV Sterilizer has little effect on the aquarium temperature.
For example, a 9 watt UV Sterilizer connected to a 100 gallon tank can at best heat your tank the same as a 9 watt heater.
With a heater 25 watts is required for every 10 degrees of ambient temperature per 10 gallons you need to raise your aquarium temperature (from Heaters; Aquarium Answers); so using this equation a 9 watt UV-C lamp (again at best) could only raise 10 gallons of water 3.6 degrees F; now divide this by 10 (since a 100 gallon tank is tens times then gallons) and you have a temperature increase of .36 degrees Fahrenheit, in other words insignificant!
(D) UV Transmittance; Other Factors Affecting UV Sterilization Pre-Filtration/ Turbidity
Another important factor that is often overlooked and sometimes controversial (as per my reading of some forums, especially reef forums) is the waters UV Transmittance. UV Transmittance which is expressed in percent (0-100%) of UVC Transmittance.
This measured value is the difference between a known UVC light source and what is measured by a calibrated detector through a 1 cm thick sample of the water to be irradiated/treated.
Water turbidity (dissolved waste particulates, DOC, etc.) in the water column, poor circulation (a poor flow pattern that has the water pickup and return too close where too much water goes unfiltered). If these factors exist and more UVC light is absorbed/blocked you will need a larger UV Sterilizer for an effective pathogen kill or green water control
The picture to the left (click to enlarge) displays UV Penetration (turbidity) and how particulate shading affect UV Sterilizer effectiveness.
Particulates in the water column interfere with the effectiveness of a UV Sterilizer by blocking UVC light and absorbing some of this energy.
For this reason, the UV Sterilizer is best placed AFTER a filter so as to remove as much particulates from the water column as possible (the UV Unit is also best placed on the exhaust/return form a filter so as to allow maximum nitrifying bacteria accumulation in a bio filter).
Sometimes this is not always possible or desirable (as per some reef keepers that feel that pre-filtration increases nitrates), in this case you MUST increase the size of your UV to compensate.
Removing as many particulates from the water prior to UV Sterilization also partly dictates what devices are better to power (move water through) your UV Sterilizer. Obviously a micron filter is going to do about the best job (other than possibly clogging faster). However most any standard canister filter (or similar pressurized pond filter)can remove a reasonable amounts of particulates prior to entering your UV Sterilizer.
Internal Power Filters or even Sponge Filters perform this task reasonably well (but not as well a canister filter).
There are also Internal UV Sterilizer Pumps with their own Sponge Pre-Filters such as the SunSun that does a reasonable job of level 1 UV Sterilization (beware of the cheapie first generation models of these internal UVs that leak and damage the UV and have poor flow rates in comparison to the wattage of the UV Bulb used). Even then, the best of this type of UV Sterilizer (the SunSun) is primarily intended for green or cloudy water control.
Your final choice would be a power head with little or no pre-filtration, while this can still work I have found that at least 20% must be taken off from the rated flow rate per watts of UV-C to make up for the higher particulates in the water when using a straight pump or power head (in many ponds this can actually cut the rated flow in half!).
Time; Generally a UV Sterilizer is best run 24/7, as this will provide the best Sterilization, Algae Control and Redox improvement. In Ponds this is particularly important as it can be difficult for a UV Sterilizer to keep up with algae growth during peak sunlight hours, while nighttime allows for a UV Sterilizer to “catch up” with algae spores. In Redox balance, a UV run constantly will provide a more stable balance.
There are exceptions though; many in Reef aquariums do not run a UV during certain hours (often using a timer) such as feeding micro planktons.
A UV Sterilizer should be turned off when certain antibiotics are added (see the next section), when seeding tanks with established filter media, or Autotrophic or Heterotrophic Bacteria are added for bio waste composting or cycling (such as cycling products like SeaChem Stability). Generally 24 hours off is long enough for these products.
(E) UVC Penetration (Microwatts second/cm2):
The emission or light intensity of a UVC germicidal light bulb is usually expressed in a term called "microwatts per square centimeter" (Mw/cm2), and can be tested with equipment such as the "General UV254SD Data Logging UVC Meter".
The maximum intensity provided by a single UVC Bulb is at its surface. So, if we calculate the surface area of the UVC lamp and only use that area which effectively emit UVC light rays, the effective area of UVC transmission will be established. Basic mathematics will show that the surface area of a cylindrical tube is ‘pie’ D L. UVC light intensity decreasingly varies as the distance from the UVC light increases.
Put more simply (a non scientific analogy); The amount of wattage will also increase penetration, as a higher watt UVC bulb will generally have more Mw/cm2. In my own experiments I have used 15 watt and 25 watt UVC bulbs in exactly the same unit (both were 18”), if wattage were only considered there would be a 60% increase in effectiveness, however I only observed a 25% increase. When I used a 30 Watt UVC bulb in a unit with over twice the exposure as the 15 Watt, the kill rate more than doubled. From my experience, if you increase wattage (and Mw/cm2) you need to also increase the volume of water to maximize the higher watt bulb.
Experiments can also be safely conducted with standard household light bulbs to correlate penetration. For this start with a 7 watt clear bulb (such as a Christmas bulb) and place varying thicknesses of paper/ cardboard in front of the bulb and measure when penetration stops. Continue this with higher and higher wattage bulbs.
This brings us back to the Dwell/ Exposure Time I noted earlier, and why the gph per watt flow suggestions that I myself use are not entirely accurate when comparing different UV units and the length, style, type of lamp used. An 8 Watt Vecton; High Dwell/ Exposure Time UV is going to outperform any 9 watt compact and often gimmicks such as "Twists" actually keep the UVC exposure way from the lamp. This is also assuming the design of the UV Sterilizer maintains a consistent .3 cm distance from the UV lamp/Quartz Sleeve at all times. This is where some designs (such as the "Twists") may fool the one into assuming a long exposure time, while in reality a good portion of the exposure time was past the most effective .3 mm range. Again, this is where a High Dwell/Exposure Time Straight Tube Ultraviolet Sterilizer shines.
UVC rays do not have great penetration ability on most substances. In the case of air, UVC has a very effective “killing” range. In the case of water (which is what we are dealing with), this can vary considerably with dissolved solids, mineral content, organic content and more. This is why pre-filtering water is important for proper UV Sterilization. Your UV Sterilizer should ALWAYS be connected after the filter, not before. Water that is still laden with minerals, organics or more will need more UVC radiation in terms of Watts and time exposure. Agitation of water being sterilized increases sterilization effectiveness.
Effect of UV Sterilization on minerals, chemicals, etc.
This is an area where a lot of information is posted in aquatic forums and similar that has little scientific proof to back up statements.
I myself have noted the affect of UVC radiation on a variety of chemicals added to treat infections and I have noted a variety of end results, HOWEVER I also have not conducted hard scientific studies nor have I found any reputable studies to make conclusive statements (although many persons do without much to back themselves up).
What I have observed is that there is no affect of UVC radiation on minerals, and many chemicals such as Malachite Green (despite comments that UVC breaks down Malachite Green I see no evidence as of writing this).
I however have seen UVC radiation breakdown some light sensitive antibiotics such as Quinine Hydrochloride.
Obviously most organic compounds are either destroyed or weakened by UVC Sterilization (at optimum levels). As I have noted elsewhere this includes nitrifying bacteria, HOWEVER this bacteria is rarely in the water column and should NOT be in the water column, so this is not a problem under most instances other than adding cycling aids (during such time UVC Sterilization should be discontinued for 24 hours).
Organic compounds also includes hormones, which can be both 'bad' (if there is a reason such as breeding where by the aquarium keeper desires these hormones in the water column) or 'good' (if one desires hormones be controlled such as for certain 'grow out' tanks). So for hormones the UV Sterilizer can be used as a tool that is turned on or off depending upon the needs of the aquarium keeper for controlling their aquatic environment.
It is however noteworthy that iron, sulfites, nitrites, and phenols can absorb UV (DeMers and Renner, 1992). This does not mean that UV Sterilizers are useful for removal of these compounds, rather that the presence of these compounds in water lower UV Penetration and thus effectiveness.
Here is a list of PROVEN light sensitive chemicals: Bromine, Oleic Acid, Ethyl Ether, Potassium Ferricyanide, Ferric Ammonium Citrate, Silver salts, Hydrobromic Acid, Sodium Iodide, Mercuric Salts, Mercurous Nitrate.
Here are a few examples for level one sterilization and basic clarification, then I will explain in more depth with even more examples accompanied by pictures.
As noted earlier in this article; for sterilization (level 1) you want 20-25 gph per watt for compact UVs or 30-35 gph for high dwell time UVs, as well as an aquarium/pond turnover rate of 1-1/2 times per hour (recommended minimum).
For simple pond clarification about 45-50 (Compact UVs), or 60-65 high dwell time UVs
Please note that pre-filtration is not factored in with these examples, as well a good circulation pattern that allows as little recirculation of the same water within the pond/aquarium into the UV Sterilizer.
These examples below ASSUME these factors & others to be within suggested parameters already discussed in this article.
Example 1: In this example I will look at the capabilities of a few UVs as per maximum size of pond or aquarium for the two most common UV applications; Clarification and Level 1 Sterilization.
*The TMC 15 watt Advantage can efficiently clarify at 60 gallons per watt, so 60 times 15 = 900 gph. Then multiple by a turnover of once every three hours which equals a 2700 gallon pond.
*The 18 Watt SunSun Terminator or Tetra Pond Green Free UV Clarifier can efficiently clarify at 50 gallons per watt, so 50 times 18 = 900 gph. Then multiple by a turnover of once every three hours which equals a 2700 gallon pond. As with the Advantage, the Tetra 18 watt can maintain a 2700 gallon pond.
*The TMC 15 watt Vecton can efficiently perform Level 1 Sterilization at 30 gallons per watt (actually higher), so 30 times 15 = 450 gph. Then divide this number by a turnover rate of 1.5 times per hour which equals a 300 gallon aquarium.
*The Jebo low efficiency 18 watt Compact UV can only provide Level 1 Sterilization at 20 gallons per watt, so 20 times 18 = 360 gph. Then divide this number by a turnover rate of 1.5 which equals a maximum aquarium of 240 gallons.
Please note that many other factors make this a generalization such as filtration, bio load, the presence of a Veggie Filter (in a pond), and of coarse the UV itself
Example 2: In this example I will use a 100 gallon aquarium (or small patio pond);
*For Clarification (Green Water Control; generally the most common application in ponds) you would need a flow rate of 40-50 gph (60-65 for some high dwell time UVs) and a turnover of aquarium/pond water through the UV of once per 2-3 hours.
So as a minimum you would need a flow rate of 50 gph (assuming once per 2 hours in water turnover). At 50 gph (for turnover) the smallest UV available is a 5 Watt which can have a flow rate up to 250 gph for clarification.
*For Level One Sterilization (generally the most common application in aquariums), you would need a turnover rate of 1.5 times per hour which would be 150 gph for this example. The flow rate through the UV should be 20-25 gph per watt (I will use 20 such as required with a Jebo UV) which would mean 7.5 watts would be the minimum UV Sterilizer (20 x 7.5 = 150).
*For Level Two Sterilization, you would need an aquarium/pond turnover rate through the UV Sterilizer of up to 3-4 times per hour, which would mean 300 gph minimum for this example.
The flow rate in gph per watt is generally 8-12 gph (sometimes even lower, we will assume a lower efficiency UV and use 8 gph per watt for this example), so at 300 gph this would require a 37.5 Watt UV Sterilizer (300 divided by 8).
With a high dwell time UV such as the TMC Vecton, @ 12 gph per watt, this same 100 gallon aquarium could utilize a 25 Watt UV Sterilizer for level 2 sterilization (300 divided by 12)
These examples also due not factor in the design of the unit as per gap between the bulb/quartz tube and the wall of the Sterilizer, as this is can require an even larger UV Sterilizer if the gap is more than .3 cm which is most often the case in many, especially pressurized pond filters and even to popular UV Sterilizers such as the Turbo Twist (albeit to a lesser extent).
Another factor that should also be considered in the length of exposure from first contact to last contact with the UV-C lamp (Dwell Time); generally speaking even the best of Compact UV Sterilizers such as the Terminator are not going to have as a long of contact exposure as the best designed straight tube UVs such as the TMC Vecton/Advantage, so the more conservative flow rates should be applied to compact UVs (especially the "twists").
*Again I want to emphasize the previously given flow rates are generic generalizations that do not take into consideration UV design, water temperature, water turbidity and more.
Water that is not pre-filtered is going to be more turbid (higher TDS) and require a lower flow rate, as well the design of some UV Sterilizers often necessitates a lower flow rate as well.
This is especially true in units with larger water volumes around the UV bulb/Quartz Sleeve as often found in Pond filter with built in UVs such as “Pressurized Pond Filters with UV”, and “Canister Filters with UV” which include many brands (this is not to say ANY of these are bad filters as they are all excellent filters, they are simply not the best way to use a UV Sterilizer in a pond!)
With all these examples, you will note that the UV Sterilizer is always after the pump and the filter.
The pump obvious has to be first to initiate water flow.
The Filter should be first for two reasons:
For one the filter removes particulates that will impede effective UVC irradiation as noted earlier in this article. As well, having the Filter first allows for establishing of necessary nitrifying bacterial colonies in the filter.
This first picture displays a pond set up whereby a pressurized filter is used along with a diverter valve to allow some water to the UV Sterilizer, and some to the Veggie/Plant Filter.
Multiple units in parallel or immediately inline with each other work well for larger ponds or aquariums.
As an example two 25 Watt TMC Advantage UVs will easily handle a 7000-9000 gallon pond. For this combination to be effective it is important to place these UVs one IMMEDIATELY after the other and connect with at least 1 inch ID Tubing for proper flow (Click the picture to enlarge)
As noted earlier there are many excellent UV Sterilizers/Clarifiers with good basic and reliable designs, however there are many excellent high end UV Sterilizers such as the Matala stainless steel UV Sterilizer that may appeal to those with large ponds with high flows. These may be a worthwhile purchase for many, however in my experience, I have achieved equal results with lower cost UV Clarifiers such as a pair of Terminator 36 watt UV Sterilizers @ $140 each ($280) connected at the proper flow and pond turnover rate as one high end UV Clarifier such as a 75 watt Matala that costs over $800; so be careful on being over sold for your pond clarification needs (as well look into improved filtration including a DIY Veggie Filter)
For more information about pond applications (including a diagram for reducing flow), please see the UV Sterilizer section in this article: A Clear Pond; Pond Information
Some Ultraviolet Sterilizers are specifically designed for aquarium use so as to maximize long UVC exposure time (& thus higher level UV Sterilization at higher flow rates) in a more compact design that fits or hangs under aquariums and cabinets.
The Vecton UV8 (V2 200) (pictured) is a good example of this design that is offers the superior long exposure straight tube design in a more compact easily adaptable design that is superior to ANY compact UV Sterilizer (including the Terminator).
Taking the very high dwell time Vecton UV a step further, the picture to the left picture demonstrates a Vecton 8 Watt UV, with a Rio 1000, Filter Max #3 Pre-Filter, 5/8" Tubing, and an Intake and Return Adapter.
This is a simple yet VERY effective way to connect a premium high dwell time UV for level one or higher UV Sterilization utilizing a simple power head and sponge pre-filter for maximum effectiveness.
The small valve included with the Rio 1000 (and many other pumps as well such as the Via Aqua 1300) can be used to slow the flow during critical times when a higher level of UV Sterilization is desired.
Here is another basic picture for plumbing a compact UV Sterilizer using an Internal Filter or Power Head.
The UV is mounted on the side only to better display how this is done; back mounting is suggested for better aesthetics.
You may also place your power head/ internal filter on its side for an easier tubing application.
The picture can be enlarged by clicking on it too!
This picture shows an Internal Wet Dry connected to a UV Sterilizer, this application also applies to the similar Bio Cube Internal Wet Dry filters (please click to enlarge picture)
Probably the most common UV Sterilizer Application is to a Canister Filter or Pressurized Pond Filter (these pressurized pond filters make an excellent alternative aquarium canister filter as well).
The picture to the left demonstrates a Vecton 8 Watt, very simply spliced ("plumbed") in-line from the return side of the Vecton UV
Fluval Canister Filters have “ribbed” tubing, which can still be used to attach to a UV Sterilizer (using Teflon tape around the UV male hose barbs and hose clamps), HOWEVER I recommend replacing the Fluval tubing with standard vinyl tubing as in the picture to the left.
Finally, a growing in popularity method of UV Sterilization for both ponds and aquariums is the Submersible/Internal UV Sterilizer. This is an excellent idea in theory that also has many flaws.
The first generation internal UV Sterilizers (which are still sold by places such as Amazon) have leakage and reliability problems as well as flow design problems. The second generation still has flow design problems.
The third generation are definitely the best as long as one understands that these still have their limits. The limits are that these still are mated to internal water pumps that are often too high a flow rate per the wattage UV-C used. You also cannot control the flow rate by virtue of mating the correct pump, diverter, valve, etc that you can with a separate UV Sterilizer.
The only 3rd generation Internal Submersible UV Sterilizer Pump I can recommend at this time is the SunSun CUP-613 & 609.
This UV Pump/Filter is also sold under another brand: HOWEVER, BE WARNED this other company also has many models that are NOT correctly mated as per pump gph and UV-C wattage and are poor at best for water clarity and CANNOT perform Level 1 or high UV Sterilization.
One major plus (or selling point if you will) is these Submersible UV Clarifiers require no additional plumbing, which for ponds often is a major hassle.
Another plus for ponds is with the 13 Watt SunSun Submersible UV is these units can be used in multiples, strategically placed in larger ponds for effective clarification; Example three of these models in a 4000 gallon pond!
These internal/submerisble UV Sterilizers are an excellent choice as a recirculating UV Filter in water reservoir such as one used to store RO/DI water or conditioned tap/well water for later use. These submersible UV Filter combinations require no additional plumbing and in the restricted/ contained environment of a reservoir, these are more than adequate for level one sterilization since the water turnover is likely quite high (such as a 30 gallon Rubbermaid type plastic trash can that I have used for this purpose).
What I would not recommend these for are inside a reef tank, especially the low end models such as the Submariner.
The reasons are for one many can more easily suck in the many minute life forms often found in the water column, especially if placed too low to the substrate. As well these are simply not effective enough for the reasons many would desire a UV Sterilizer in the first place, again especially the low end models such as the Green Killing Machine as all these are good for is clarification and frankly I have yet to see a reasonably well maintained reef aquarium with clarity issues!!!
For help in connecting aquarium tubing to hose barbs or similar connection
please click this picture.
Is Too Large a UV Sterilizer a Problem?
This is an occasionally asked question to which the answer is generally no with some exceptions.
In my view spending more for say a 36 Watt UV connect with a 300 gph water pump flow will produce 8.33 gph per watt, however this does not generally produce much better results than 20 gph per watt. While it may be true that parasites such as Cryptocaryon (marine Ich), are more readily killed at this rate, this is not an established fact either (as of writing this). I find that UV Sterilizers help control Ich or similar parasites not by killing them, but by improving water quality such as Redox which in turns improves the fish’ natural resistance allowing treatments or other measure to eradicate a given parasite infestation.
As well in a marine reef tank in particular, this high wattage to flow ratio may kill copepods or other propagated organisms (assuming they get into the water column, which is rare). While the facts that many of the organisms propagated in marine reef are not killed by typical UV flow rates (20 gph per watt), making it a myth that UV Sterilization should not be used in reef aquariums, I would also not push the envelope with flow rates under 10 gph per watt.
Another aspect to consider with low flow rates per watt (generally under 10 gph per watt), is that I have often found that with commonly used UV Sterilizers that the aquarium turnover rate is affected which is another important aspect of UV Sterilization. With the above example of the 36 Watt UV and a flow rate of 300 gph on a 100 gallon aquarium would not be a problem. However lowering flow rate to 50 gph (so as to maintain 10 gph per watt) with a 5 watt UV Sterilizer would considerably lower UVC effectiveness in this same 100 gallon aquarium.
This all said, if you do not have a marine reef aquarium, just a fish or plant only aquarium and feel more secure with a flow rate of 10 gph per watt, by all means go for it, but generally this is just money wasted in my experience.
WHAT IS A QUALITY UV?
As noted earlier in this article; Proper UV sterilization starts with contact time, water turnover, water turbidity/filtration, water temperature, bio load, and more.
Many UVs now available do not have proper contact time or advertise too high a flow rate.
As noted in other sections of this article, 20-30 gph per watt of UVC for level 1 UV Sterilization (40-50 gph for Green Water). As an example, a Custom 15 watt UV I personally have built is effective when installed properly (in part because it is flow restricted and will not allow more than 350 gph necessary for level 1 UV sterilization).
UV sterilizers that place the UVC lamp above the water are generally less effective, again due to poor UV-C exposure (I have used several such UVs over the years).
Be careful of some of the cheap UV sterilizers currently flooding the market generally for under $50 usd, such as the Aqua Medic, Sunterra, etc.
Our aquarium/pond service experience has had poor results with these units (leakage, poor sterilization patterns, low quality ballasts, & more).
If you obtain one of these units, you CANNOT make a fair assessment of what UV Sterilization can really do.
Other designs of UV Sterilizers that have been around before (as far back as the 1970s) are those that mount to Under gravel filters and "Hang on the Back Filters". Nektonics was one of the first manufacturers to experiment with these ideas (I too used and tested these in the late 70s and early 80s). The problem is not usually flow rate, rather a poor design that does not allow for correct turnover, exposure distance from the UVC lamp, and contact. While these may seem like a good idea (I thought so too), in practical test these all failed level one sterilization tests, yet alone level 2 sterilization which is claimed, but impossible simply based on flow rate, if not dwell time).
One such new reincarnation of these already tried (but failed) ideas are the Hang On Filters With UV (pictured to the above left), such as the PFUV-25, PFUV-40, & PSE1.
Also beware of the a basic Internal UV Sterilizer imported out of China, first by Jebo now called the Killing Machine.
We thought this to be an awesome idea ourselves, however after testing they failed miserably with not one of these Internal UV Sterilizer passing durability tests. What is sad is that they are now being marketed as the Killing Machine after most reputable aquarium maintenance companies & retailers have since rejected the originals. The bottom line is if the UV seems "too cheap", there is most likely a good reason such as with the PFUV-40 Hang on the Back Filter with UV at price of $50;
For $50 you are not going to get an effective filter and most definitely NOT a Level One UV Sterilizer!!.
Effective UVs include the TMC Vecton & Advantage (easily the best when all factors are considered including price), the Cyprio, Aqua UV, and the Emperor.
Among the Compact UVs; the Tetra and the SunSun Terminator UV Sterilizers, while not as good as the before mentioned high dwell time premium UVs are still an excellent UV.
The SunSun Internal is the best of the Submersibles.
Even with many of the before mentioned UV Sterilizers/Clarifiers, many although of good design and reliability, are often over priced or imply features that add no effectiveness to actual sterilization effectiveness.
An example is the Tetra Pond UV Sterilizers, such as the GreenFree™ UV Mini Pond Clarifier; which is over priced and yet less effective than the TMC Advantage models.
Although reasonably well made, this 5 watt Tetra UV adds no more effectiveness than a SunSun Terminator 7 watt UV Sterilizer (a Compact UV of similar design).
In fact you will likely pay twice as much for the Tetra over the Terminator only for a slightly thicker plastic housing, and despite some common perceptions, neither should be kept in direct contact with weather and both are only water resistant, not water proof.
I will also add for pond applications, generally a 5-7 watt of any brand is too small but for the smallest of water features. I generally recommend 13 watts or larger, and even then the TMC line of Advantage UVs is far more effective/efficient for ponds than ANY compact UV design.
If heavy duty UV Sterilizer construction appeals to you (generally for pond use), rather than the Tetra Pond Green Free UVs, I would suggest the TMC Pond Advantage such as the TMC UV-25 Pond Advantage. TMC (Tropic Marine Centre of UK and Germany) is the European leader in aquarium technology, including UV Sterilizers and unlike the Tetra Model you will also be purchasing a HO straight UVC bulb with much better UVC exposure time for a better price than the Tetra Pond UV 18.
The TMC Pond Advantage UV15 and UV25 is the heavy duty (albeit more bulky) version of the TMC Vecton UV15 & UV25 and is excellent for Aquarium use as well as pond use. That said the Vecton UV8 & UV15 are specifically designed for aquarium use with a design that provides full size UV flow capabilities along with a design that fits better in many confined aquarium cabinets, etc.
For larger pond or professional use, the TMC 110 Watt PRO UV is without equal (nor gimmicks such as wipers or twists)
The bottom line is if you are looking for a “High End” UV Sterilizer/Clarifier, the TMC line of UVs is without equal when performance/effectiveness, durability, and price are all considered.
I would be aware of otherwise good Pond Filters such as the Clear Steam Pressurized Pond Filter and many others such as Cyprios & Tetras. As well as some new Aquarium Canister filters that come with built in UV Sterilizers in the top (such as the Grech, SunSun, and related canister filters). These are rarely as effective as a separate unit for these reasons;
*Flow rate is often too fast for proper contact/exposure and rated wattage to generate the correct temperature around the bulb.
*The water in these style units is not contained in a small space around the UVC bulb (less than 3 cm) rather the flow is in a large area around the bulb which is generally not adequate for good UVC exposure/ dwell time.
*Many pressurized pond filters and aquarium canister filters are not 100% in their internal flow patterns, meaning a certain percentage of water that passes through the filter is never even routed next to the UVC lamp, UNLIKE a separate UV Sterilizer!
It is always best to purchase a separate UV sterilizer that can handle the flow rate as per its wattage or divert the water through a ‘T’ Valve to the UV at a slower flow rate than the Filter or main pump is running at. While I personally sell and use TMC Clear Stream Pressurized Pond filters and SunSun Aquarium Canister Filters, I want to make it clear that while these are good filters with many selling points, the additional UV Sterilizer is more of a gimmick and should not be part of your decision to purchase or not to purchase.
Finally be aware that although HO (high output) UVC lights are certainly an improvement over a similar length UVC bulb of similar length, they do not increase effectiveness proportionally as to wattage per length. Often HO bulbs are very short and even with this higher output, these are often still not enough for the water flow that is usually applied to these UVs.
For example, although an Emperor with a 50 Watt HO bulb of 18 inches will handle a higher water flow than a 25 watt UVC bulb found in a Sterilizer such as the TMC Advantage; the flow rate is not doubled.
Better combining two 25 Watt TMC Advantage UVs for double the exposure time over a 50 watt UV with only 18 inches of straight tube UV-C lamp exposure (see the picture in the "What Size UV is best section").
Or a unit with long exposure such as the TMC Professional 110 Watt UV Clarifier as compared a Smart HO Two-Lamp 100 Watt UV Sterilizer. The TMC Pro 110 Watt is not only vastly less money, it is a superior UV Sterilizer in terms of UVC exposure and performance!.
As a side note, I as the author of this article (which not only represents 1000s of hours of research, but many years of practical use and controlled tests) obviously hope to sell a quality UV Sterilizer that I choose to make available on my web site (of which the mark up is extremely low so as to make them more readily available).
This does not discredit the research and experience that has gone into this article, nor does this mean that there are not many good UV Sterilizers available elsewhere (such as Aqua, Emperor, etc.). However I choose to recommend UV Sterilizers I would use myself for my clients based on quality AND value (many excellent UVs are over priced for what they provide in capabilities IMO). It is also noteworthy that there are also several UV Sterilizers that are of poor quality that are not worth purchasing at ANY price (I will leave mentioning most of these to my blogs)
UV STERILIZER MAINTENANCE:
UV Sterilizer maintenance is quite straight forward; make sure you keep your unit dry on the outside, if used for a pond try and protect your unit from harsh weather (most sterilizer can withstand the outdoor environment, they just last long if they can at least be partially sheltered). Bulb: Change your bulb every 6 months for aquariums, and also every 6 months for ponds in warm climates where there is no winter freeze.
In cool climates a pond UV bulb can be changed every season (usually late spring/ early summer), however as your pond UV Sterilizer approaches a year, your UV-C Lamp is only emitting about 25% of the correct UVC energy, so changing a pond UV bulb once per year say in Sept. will not be of much benefit since it will be very inefficient when you need it most (the warm/hot months of summer).
It is also noteworthy (based on my experience), that a so-called "long life" UV Replacement bulb is a marketing ploy. The facts are that while these might "burn" longer, these are also a lower output UV-C lamp and thus defeat the purpose to use. My point is do not fall for this marketing ploy; purchase an Optimum 254nm High Output µW/cm2 UV-C Hot Cathode Quartz Germicidal Bulb and change it every six months for aquariums and warm climate ponds and once per year for cool climate ponds!
Quartz Sleeve; If your UV has a quartz sleeve it is important to clean the quartz sleeve when changing your bulb, otherwise your bulb change will not be very useful. Be very careful when cleaning a quartz sleeve as they are very fragile and expensive (and usually hard to find replacements). I recommend cradling the quartz sleeve in a pillow while cleaning and using acetone to remove scum and other deposits (not glass cleaner).
Some UV sterilizers come with wipers which are used keeping your quartz sleeve somewhat clean between bulb changes, however they are more of an expensive gimmick (my experience with them is they do little to remove build ups that block UVC light) and still do not take the place of cleaning your quartz sleeve at bulb change time.
Be careful when simply changing aquarium water (or bulbs) to not let your UV Sterilizer run dry WITH the UVC Lamp/Bulb still turned on.
What can happen is the Quartz Sleeve will heat up and then when water is re-introduced to your UV Sterilizer this can and often does crack your quartz sleeve. If left running with this crack (which may not be easy to notice), this will damage electrical components to the point where the UV is NOT reasonably repairable at a cost less than a new UV Sterilizer.
Another important note is that many UV Sterilizer manufacturers do NOT make their Quartz Sleeves available to retailers at reasonable prices; the result is if your Quartz Sleeve is broken beyond repair (sometimes small cracks can be repaired with a small bead of silicone on the outside of the Quartz Sleeve), it is simply cheaper to replace the entire UV Sterilizer. This is especially common with lower efficiency Compact UVC Sterilizers (these use the G23, G11, G24, PLL, PLS type UV replacement Bulbs).
If you find yourself in this situation, I STRONGLY urge readers to purchase a UV Sterilizer of higher quality with better efficiency/dwell time such as the TMC Advantage/Vecton UV Sterilizer/Clarifier line. TMC is well known as a company (especially in Europe) that not only builds premium products, but ALSO supports their products with replacement parts at reasonable prices!!
Ballast/Transformer; This part of a UV Sterilizer, Purifier, etc. often does not last as long as the main body/unit itself. This is more true of the electronic ballasts than magnetic (although the starters used with magnetic ballasts often need to be changed every year), as well many of the low quality units that are now flooding the market often have cheap electronic ballasts that last 6 months to a year. Poor design, care, or placement of a UV Sterilizer/Purifier can also prematurely destroy an otherwise good ballast.
The use of a multi-meter is the best BASIC way to check a ballast. Assuming a 120 V connection (North America), the output from the ballast should be 120 Volts A/C, while your Amps should be about 2.23 Amps (AC/DC), and your Ohms should be about .75
HOWEVER this basic multi meter test only takes into consideration basic electrical power to run the UV-C Bulb/Lamp, not the shot of high-voltage electricity (500 plus volts) ignite/ionize to the gas within the fluorescent bulb; there is NO way that I know to test this function if you have an electronic ballast (magnetic ballasts utilize an easy to replace starter to perform this function).
With magnetic ballasts, make sure to check the starter first, as magnetic ballasts can often last for 25 years while the starters often last six months to 2 years (a fluorescent starters function is to send a delayed shot of high-voltage electricity to the gas within the fluorescent bulb).
FACTS (& MYTHS) ABOUT UV STERILIZATION;
Here are few things UV Sterilization will NOT do:
 UV sterilization will not cure infected fish of bacterial or fungal diseases. A UV can aid in cure by killing bacterial pathogens in the water column and fungal spores, also by improvement of the Redox potential (which is much more important than many realize based on scientific research) and general water quality.
 A UV sterilizer will not kill ich trophozoites already on the fish (but then medications don't either), but UVC can again slow the spread of ich tomites in the water column (but usually not out right kill ich tomites). However by water quality improvement (such as Redox Potential) and lowering of pathogenic bacteria, the fish has more natural resistance to fight Marine Cryptocaryon or FW Ich.
 A UV sterilizer will not kill beneficial bacteria such aerobic bacteria, as this bacterium is effective when attached to a surface of high water flow such as the sponge of a sponge filter, not when in the water column. In fact relatively new scientific evidence shows nitrifying bacteria to be sticky and adheres to the surfaces like glue this is why the myth of UV Sterilizers killing beneficial bacteria is just that, a myth. It still may be best to turn off a Sterilizer unit when introducing bacteria in liquid form to seed a new aquarium.
 UV Sterilization will not remove or destroy algae growing on tank or pond sides, rocks, decorations, etc.
However UV Sterilization can aid in the spread of certain algae that utilize spores as part of their mode of spread/replication.
Certain problem algae such as hair algae; most of the time hair algae comes attached to the plant that was purchased, or it may come in attached to the shells of snails or similar transferred rocks, etc. Unfortunately for this type of algae, you find little aid from a UV Sterilizer.
See: Aquarium or Pond Algae
 UV Sterilization will NOT kill off copepods and other small life forms in a Reef or Nano Reef Aquarium.
This is one of the more laughable myths about the use of UV Sterilizers in reef aquariums as these copepods live at or near the bottom of live rock piles (making a pile with small pieces is best for copepods), they are not active in the water column. If properly installed, the UV should have at least a fine pore sponge filter media as a pre-filter, which will further stop the “ingestion” of these and other minute life forms (the UV benefits as well by being more efficient). What is interesting about this myth is that many who spread this misinformation use filters such as the Ocean Clear Micron Filters systems (which are excellent micron filters), these filters will filter out any copepods that get caught up in the water column and “sucked” into the filter. As well even “pods” that do manage to find their way into the UV Sterilizer are rarely killed due to size as the typical flow rate of 20+ gph is not low enough to kill them (you would need at least 10 gph per watt, which I do recommend running a UV Sterilizer at flow rate of under 10 gph per watt for this reason).
The bottom line here is that I have maintained MANY Reef aquariums with UVs with growing copepods, anemone and other creature populations. Honestly this is one of the worst urban myths in the aquarium hobby about UVs (mostly spread on the internet in misinformed forums which never conduct or read scientific evidence to back up these absurd statements). The only truth to these statements is that UV Sterilizers can destroy some microscopic food sources needed by some of these organisms (usually planktonic algae, although timers that turn the UV on during certain hours is an easy remedy for this possible problem).
 UV Sterilization NOT remove minerals from aquarium water, however UVC Sterilization will also aid in the removal of oil based (carbon based) pollutants.
 The use of Ultraviolet Sterilizers will NOT lower fish immunity, in fact from my many controlled studies, the opposite is true. Although the exact mode is theoretical, evidence points towards improved Aquarium Redox being at least part of the reason.
See also this article: “Fish Immune System and UV Sterilization”
 UV Sterilization will NOT make up for poor aquarium maintenance practices such as over crowding, over feeding, inadequate filtration, poor cleaning practices, improper water parameters, and more. This point is likely the cause for anecdotal statements that fish coming from tanks that had UV Sterilization, then are placed in a tank without an Ultraviolet Sterilizer resulting in “losses” may be dealing with (besides the above point of improved immunity, which will be lowered after transfer). Often an aquarist (I have also performed this as well for studies) will rely too much on the Sterilizer/Clarifier for water quality, clarity, etc., as a UV Sterilizer will often keep a tank clear and healthy in appearance even when correct water changes, mineralization, etc. are not performed. For this reason the fish may not be has healthy as they should since a Sterilizer should NEVER be relied on as a replacement for good aquarium maintenance practices. Along this same line of thought, often aquariums maintained this way will have low KH and falling pH which can result in osmotic shock and even death when transferred.
 UV Sterilization is only useful for water clarification; This myth is unfortunately perpetuated by the tidal wave of low cost UV Sterilizers from companies such as Submariner, Green Killing Machine and more.
What happens is users (often based on non-scientific reviews on Amazon or aquatic forums) will purchase these and find reasonable clarification results (even then not always), but find no improvement in Redox Balance, Fish, & overall aquarium health. These persons will then write about this anecdotal observation in forums, further reviews, Yahoo Answers, etc further perpetuating this myth.
Hopefully any reader has already figured out the lack of scientific truth to this myth after reading this far in this article.
See Also: Green Killing Machine, Submariner Review These are best for water clarification ONLY.
 UVC Light energy will not penetrate a plastic or pvc shell of a UV Sterilizer; even a clear or transparent plastic viewing window, hose barb or similar does not allow the passage of UVC light energy. All you are seeing is blue light.
This is why quartz is used for the sleeve versus plain glass as even "plain glass" blocks the majority of UVC light energy!
IN DEPTH INFORMATION ABOUT UV
THAT FURTHER EXPLAINS THE PROPERTIES OF UVC STERILIZATION:
All gases, liquids, and solids are made up of elements. The fundamental building blocks of elements are atoms, which in turn are made of electrons, neutrons and protons..., all held together by electronic attraction. This is referred to as polarity, the principle that positive and negative poles attract and remain bound together based upon the strength of that attraction. There are over 100 elements known in our universe. It is the elements that form compounds.
Elements combine to form gases, liquids or solids. For example, water is made of two molecules of hydrogen and one molecule of oxygen. Carbon dioxide is one molecule of carbon and two molecules of oxygen. These and all other combinations of elements are bound together by the force of attraction or polarity at the level of the atoms. Organic compounds. The compounds of our focus are those structures that are organic in nature. Primarily it is the organic molecules that are the basis of indoor contamination.
We need to understand these compounds so we know how to clean and purify the home. Organic compounds are carbon based. Life is determined by carbon based DNA and amino acid chains. Carbon is not only found in "life," but a whole range of chemicals. A number of useful organic compounds are made up of carbon, nitrogen, hydrogen, oxygen and traces of other elements. The most recognizable organic compound is based upon the carbon and hydrogen combination, or hydrocarbons. Plastics, petroleum products and gasoline are hydrocarbons. Hydrocarbon Organic compounds tend to break down or decay faster than non-organic. The decaying process means hydrogen and carbon molecules separate.
For example, if the plastic (organic) in milk bottle is left in the sun for a couple of years, much of it will decay. Skin, hair, tissue (all organic) decays more rapidly. This also shows the effectiveness in UV Sterilization in removing oil based pollutants from an aquarium.
With the understanding that carbon is the building block of life (and more), we now need to look at the forces that will break down organic and carbon based contaminate molecules. In short, a photochemical process, initiated by short-wave ultraviolet can do this. Short-Wave Ultraviolet we all accept but don't understand the damaging effects of x-ray and gamma ray radiation. Why isn't visible light as destructive on human cells or bacteria as x-ray and short wave UV have been shown to be? X-ray, gamma, ultraviolet, infrared and visible light energy all fit in a category called "electromagnetic" energy. They all have the same characteristic "lazy S" energy wave, that travel at the speed of light. The light ray energy is called photons that oscillate, resulting in wave frequency. The difference in each type of wave energy is the wavelength, the distance across this wave. By definition, the shorter the distance across the wave, the more powerful the wave will be. The difference in the wavelength determines how the wave affects its surroundings. It is this wavelength difference that allows short-wave x-ray to pass through walls, while longer-wave visible light cannot pass though the same material; short-wave ultraviolet and x-ray can destroy DNA in living microorganisms and breakdown organic material while visible light will not.
Nanometers: Measuring Light Energy All light energy is measured on a "nanometer" (nm) scale. Nanometer means one-billionth of a meter. The lower end of the scale has the shortest wavelength, and the upper the longest. Cosmic, gamma, x-rays and "C" band UV are all classified short-wave energy. Visible light is at middle ground, at 400-700 NM on the scale. Infrared light is in the upper end of the spectrum, running from about 800 to 1400 NM, and radio waves are longer yet in the 1400 to 2200 NM range.
Ultraviolet light is toward the low end of this scale, from about 100 to 400 NM, with three categories, "A," "B" and "C." UV is beyond the range of visible light and cannot be seen. We only see evidence of its presence. Short-wave UV, called "C" band (100 – 280 NM) is known as UVC. Most C band radiation is screened from the sun before reaching the earth by the production of ozone in the upper atmosphere. Useful UVC is entirely manmade, found in today's low-pressure UVC lamps. The most effective sterilizing range for UV is within the C bandwidth. This range is called the germicidal bandwidth. The ideal germicidal curve is considered 240 NM to 280 NM, with the most effective at 265 NM. With the initial exposure, UVC has properties that alter the cells of living tissue, particularly microbes. UVC radiation triggers the formation of peptide bonds between certain amino acids in the microbes DNA molecules. This renders bacteria, viruses and molds harmless by robbing them of the ability to reproduce. Most research points to a microwaves per second by cubic centimeter (mW/cm2) of 4,200 to 8,700 to destroy bacteria of their ability to reproduce. (please see the next section for more about mW/cm2)
If the germ cells are exposed for longer periods, they start breaking down to the molecular level (carbon, oxygen, hydrogen, nitrogen ions, etc.).
UVC Germicidal Effectiveness Wave length; NM Relative germicidal effectiveness
The optimal wavelength for germicidal effectiveness is shown to be 265 NM
Aquarium & Pond UV Sterilization Summary
This article is quite in depth, especially when one reads all the outside references/sources.
However if one conclusion/summation can be honestly be made by reading this article and the resources in their entirety, that is that although one CAN maintain a healthy aquarium or pond without a UV Sterilizer, adding this device greatly increases your chances of success and when one considers the price of many UV Sterilizers vs. the cost of replacing valuable fish, not to mention time, possible remedies, and heart ache it is often foolish to dismiss a UV Sterilizer as an irrelevant piece of equipment.
OTHER USES FOR UVC:
UVC Sterilization is not just limited to Aquarium and pond use. The use of UVC Sterilization is growing in popularity for use in foods and food preparation. UVC is also used for Indoor air quality as a means of purifying the air that we breath, removing harmful pathogens from the air.
(I am posting this here to make readers aware that although UV Sterilizers are not essential, reasons such as this are poor ones to not have a UV).
I was going thru Yahoo Answers, as I was curious about this feature.
I stumbled upon this gem;
What is the best UV Sterilizer for use in a 20 gallon tank and where can I order one online?
A UV sterilizer might do more harm than good to a 20 gallon tank. The UV sterilizer will do exactly that; sterilize almost everything that passes through it, bad bacteria and the good. In a 20 gallon tank your water will circulate so many times that you may be doing more harm than good. There are other ways of treating the water in your tank that might not be has extreme as a UV sterilizer.
TOTALLY AND COMPLETELY WRONG!
This a good example where caution needs to exercised not just on the internet, but at many so-called aquarium stores staffed by un-knowledgeable aquarists. This person probably has never even used one to make such an outrageous statement such as this.
Often many aquatic forums are staffed by after work aquarium “experts” who have not done their homework or worse, they are just plain dishonest. (This is not to say there are not a lot of good ones out there, but I have left a few after being flamed there by aquarists who knew nothing about which they were talking about).
I have spent 30+ years studying, reading, and doing tank by tank comparisons in my aquarium maintenance business. A UV should be properly installed such as not to high or slow a flow rate. Also the watts per gallon have to be figured.
Another often missed aspect is the Redox Potential which research shows having a balanced Redox Potential improves the water quality much the same a way an anti-oxidant vitamin works. A UV sterilizer properly installed helps with this!
Also in studies with goldfish (a fish with a higher impact on bio load), I have found vastly healthier fish in aquariums with UVs versus without, with all other aspects such as feeding and filtration equal.
Another incorrect point was about the “good and bad” bacteria. Aeromonas bacteria are common in most all aquariums and pond they are only “bad” when they become pathogenic due to an injured or weak fish, or very common, when water conditions are poor. “Good” bacteria such aerobic nitrifying bacteria can be “bad” when there is a bacterial bloom, as they rob oxygen from the fish, weakening fish even more for other pathogens. In both scenarios, UV Sterilizers can help control.
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Finally here is a demonstration video for the installation of a UV Sterilizer to an aquarium using a power head or internal filter:
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