AQUARIUM:

Start with as large an aquarium as you can afford (even for bettas).
The very BASIC principle is to have 1 inch of NARROW bodied fish per WELL FILTERED actual gallon of water is a starting point, but not very accurate. This also only applies to a standard rectangular aquarium.
Goldfish have a higher impact on the bio load with more body mass per inch (being grazers they ounce per ounce produce more waste), so I would triple this with them, in fact for long term goldfish health, one goldfish per 8-10 gallons is best (One goldfish per 30 liters).

Obviously longer fish need more tank width and length. I would decrease the amount of fish proportional to the gallons in a tall aquarium or hexagon aquarium. Remember, many fish purchased can grow much larger than your original purchase size (ex: goldfish), so keep this in mind too.

* To figure your tank size get your tank length, height, and width in inches then apply this formula (multiple all dimensions):
L x H x W = X; Then divide X by 231
This gives you exact gallons of the tank. In round tanks or unusual shapes you will have to extrapolate.
To convert gallons to liters multiply by 3.785
(Ex. a 20 gallon tank = 75 liters).

What is much more important in determining how many fish you should add to your aquarium are these factors:

• The amount of surface area relative to the gallons of water the aquarium holds. I have observed many tall narrow aquariums over the years of my maintenance service where the filtration and other factors were equal to comparable sized and stocked rectangular aquariums, that general fish health and longevity were lower.
• Type of fish, such as fish that naturally produce more waste (partly due to the type of food they eat) such as goldfish which are grazers with less efficient digestive systems. As noted earlier with goldfish one fish per 8+ gallons is suggested.
  Also a fish, such as an Arowana, that stays primarily on the surface will need a disproportionately large aquarium (I recommend 200 + gallons for just one Arowana).
• Body mass per inch/centimeter. The actual weight of a fish has more bearing on the aquariums capacity than the length. Many high capacity bio-filters such as the TMC Fluidized Sand Filter actually are rated by weight of the bio load with the #1500 model rated for 30 lbs. of fish or other inhabitants.
  For instance, you cannot compare a heavy bodied cichlid for instance to a narrow bodied tetra of similar length. AS well a tiny Bamboo Shrimp with very little weight is going to have very minimal impact on the bio load and thus the capacity of the aquarium.
• Filtration, a properly filtered aquarium (good bio filtration, good mechanical filtration, and good circulation) with multiple filters is important. Good bio filtration (such as Sponge or Fluidized Sand Filters) with well maintained filters can go a long way in allowing an otherwise small aquarium to hold more fish or a large tank maintain a healthy "Monster Fish Tank".
• Maintenance schedule that includes regular efficient water changes.
• Well maintained water chemistry, including GH (mineral ions), KH and Redox not just low ammonia, nitrites, and nitrates.
• New or experienced aquarist; a new aquarist needs to start with a much less crowded aquarium.
• After proper feeding, good cleaning routines (20% water changes with a gravel vacuum once per week or two), proper feeding routines, good filtrations; If after all these are checked off and you still have nitrates that struggle to stay below 40-50 ppm, you probably have an over stocked aquarium (especially if there are live plants!). Also a kH and pH that starts out at proper levels, but then drops quickly after water changes and/or addition of stabilizing chemicals/buffers can indicate over stocking (as well as other problems such as mulm buildup).

SUBSTRATE;

For the average aquarium I recommend 2-3” of #3 or pea sized gravel. This allows for less build up of hydrogen sulfide producing anaerobic bacteria. The down side to larger gravel is that it will allow for more waste particle or eaten food to accumulate. With proper maintenance though, waste accumulation should not be a major problem. Sand is good for heavily planted aquariums, as it provides a better anchor for the roots and even more important sand traps nutrients and symbiotic bacteria needed by plant roots. If used for live plants, I recommend about ½” #00 or #1 sand followed by 2-1/2” of medium (#3) gravel, with substrates such as SeaChem Flourite or Eco Complete mixed in around plant roots. These two products can be substituted totally for gravel or sand (Although that can get pricey)

If your aquarium is going to be only lightly or moderately planted, I recommend sand only in the area around the plant roots and #3 size gravel elsewhere (otherwise you may develop Hydrogen Sulfide producing anaerobic bacteria).

Consider mixing different types of natural or colored gravels to achieve a look you like.

For hospital, breeding, or heavily populated temporary holding tanks; no sand or gravel is best. This allows for less waste build up, less possibility of waste matter or substrate absorbing medication in a hospital tank, and less rotting organic sludge in a holding tank.

For a little more info about substrate, please read this article:
Aquarium Gravel, which size?

FILTERS/ PUMPS:

• 5 times for an average non-planted freshwater aquarium
• 2-3 times for an average planted freshwater aquarium
• 2-3 times Betta or Fish Fry Grow-Out aquariums
• 6-7 times for high bio load aquarium such as a "Monster Fish" aquarium

HEATERS & WARM WEATHER COOLING:

Most tropical fish do well at a temperature between 76 and 80 degrees Fahrenheit. (Discus prefer warmer).
Goldfish do not need a heater.
I recommend 25 watts for every 10 degrees of ambient temperature you need to raise your aquarium temperature. EX: If your home is 68 degrees and you have a 40 gallon aquarium, to reach a temperature of 78 degrees you would need a 100 watt heater.
Also remember that bettas are still basically tropical fish too, so if they are kept in a bowl try and keep them in a warm area of your house, preferably above 70 F. A light does not pass for a heater, you cannot leave your light on 24/7 (an exception would be an Infrared reptile lamp, which are great for bettas).

If your temperature fluctuates between night and day, even though you have the correct wattage heater, you may have an “Automatic” heater vs. a “Thermostatic” heater. Usually the cheaper clip on the back are automatic heaters; they respond to a setting (two contacts that are tightened for more heat), not by temperature. These heaters generally turn on and off at the same rate whether it is summer or winter (which is why they need seasonal adjustments). The best heater will have a separate temperature probe such as most Titanium heaters. For some examples of Thermostatic Heater, including Titanium, please see: Aquarium Heaters

For more about aquarium heaters, please see this article in my Aquarium Answers Blog: Aquarium Heaters; Preset vs. Non-Preset

Cooling; sometimes cooling a tank in the warm summer months can be an issue, and most freshwater aquarists cannot afford an expensive chiller (which can cost $500 +). A few suggestions include floating frozen 2 liter plastic pop bottles in the aquarium and the use of a wet towel draped over the tank with a fan aimed at this towel (this works similar to human perspiration). The wet towel/fan method is more efficient for larger aquariums and tends to have less temperature swings, however sometime the frozen bottle method is needed for quicker lowering of temperature; as well both methods can be combined. I often had clients leave a wet towel & fan on their tank before leaving for work, then add a frozen bottle when they come home.

Other options can simply be to add a small room air conditioner and set it at a high setting of 78 F. This can often be cheaper than both the purchase and operating cost of an aquarium chiller in my experience.

WATER CONDITIONING:

If tap water is used it will have to be treated to remove chlorine or even chloramines and heavy metals. Products such as “Start Right Water Conditioner” can remove chlorine and some metals and also break the ammonia/ chlorine bond in chloramines and remove the chlorine but leave the ammonia. “Prime”, Amquel Plus, Ammo Lock or similar products are good to use in municipalities where chloramines are used in tap water.
SeaChem Prime or Amquel Plus are excellent first choice products to use when ammonia and nitrite levels are an issues, as these do not interfere with the cycling process as other products can.

RO (Reverse Osmosis) water can be used IF minor elements and electrolytes are added. NEVER use straight RO water or even worse, distilled water.
For MUCH more information about tap water, please read this article:
“What should I know about tap water for my aquarium? From Chlorine and Chloramines to Phosphates”

Salt is also commonly added to freshwater aquariums as a disease preventative, slime coat stimulant, or simply due to requirements by certain freshwater fish such as Livebearers or African Cichlids to have salt present the water. Generally 1 tablespoon per 5 gallons (35 liters) of water for a community tank is what works best. However this amount may be increased to double this for many livebearers such as mollies (please note that mollies need much more than salt such as calcium and other elements, I recommend reading this article for more information: “Mollies in Aquariums”).
It should also be noted that some catfish (such as Cory Cats) are very sensitive to salt and care should be given in use of salt when these fish are present. Salts (and not just NaCl) do not evaporate and only small amounts are depleted by normal life processes of aquarium inhabitants, so slat should only be added back during water changes and ONLY for the amount of water removed (changed) to prevent accumulation.

CYCLING:

Your aquarium will not be at peak biological filtration for 6 weeks (or more). To start your biological filtration, there are many cycling products available, many such as “Cycle” by Hagen are made with Heterotrophic Bacteria instead of the proper Autotrophic nitrifying bacteria. My success with these products is mixed at best.
A better cycling product would be SeaChem Stability which is a blend of synergistic blend of aerobic (including encapsulated oxygen) and facultative bacteria. Even then this product should not be depended upon as the sole means of nitrogen cycling.

I prefer to add gravel and/or used filter sponge or cartridge from another aquarium.
This method of adding media is much faster (you still have to take it slow), and provides all the necessary bacteria, the only negative is adding disease pathogens to your aquarium, but I have rarely encountered this problem.
If you add plants (many such as hornwort remove nitrogenous waste), you can stock somewhat faster as the plants will remove ammonia too. We used this method for our Aquarium Maintenance route for years and never lost a fish to Ammonia or nitrite poisoning.

Another method is fishless cycling include adding fish food to bring your ammonia to about 4-5 ppm or the use of un-scented ammonia where it is added into the aquarium (3-5 drops per gallon pure ammonia) so as to bring your ammonia level to 4-5 ppm. It then takes about 2-6 weeks for the aquarium to cycle.

Cycling is what is referred to as the Nitrogen cycle. Waste (nitrogenous) from the fish is broken down first from ammonia (NH3, the most toxic) to nitrites (NO2, less toxic) to nitrates (NO3, least toxic- but high amounts can stunt fish growth and lower disease resistance).
At a pH of 6.5, NH3 (ammonia) converts to NH4 (ammonia) which is basically non-toxic to most fish (many ammonia removing chemicals to a similar ion change, as they do NOT actually remove ammonia). If you have plants in your aquarium they will directly consume the ammonia (especially hornwort), thus rendering the NO2 (nitrite) part of the nitrogen cycle null. The danger here is if your pH climbs above 6.5 the ammonia can change to much more toxic NH3 and the aerobic bacteria needed for nitrite consumption will be sparse.

Aquarium cycling is a VERY important topic (more so for a beginner) and I highly recommend reading the FULL article below about The Aquarium Nitrogen Cycle. This article will go into MUCH greater depth about all aspects of cycling and explain the truths and myths as well: Aquarium Nitrogen Cycle and Cycling

CHEMISTRY (& TEST KITS):

First, please note that this section is a VERY brief and basic outline of freshwater aquarium chemistry; for any aquarium keeper looking to go beyond just very basic aquarium keeping, please read these articles:
* Aquarium Chemistry (This article has a basic suggestions section near the end that is worth reading.)
* Osmoregulation in Fish; Minerals; Use of RO, Soft Water for Aquarium
* Aquarium Nitrogen Cycle

Next, it is generally helpful to know your new water source parameters (tap water, etc. used for filling your aquarium). This will help you make what is generally only minor adjustments to your chemistry with buffers and mineral supplements.
Keeping exact GH, KH, & especially pH is for advanced fish keeping and should should not be attempted until an aquarium keeper has a clear understanding of aquarium chemistry.

Summary of "Numbers" to Maintain:
*Ammonia/Nitrites; 0
Very toxic even at low levels, should be kept at or near 0 Please see this article for more about lowering ammonia and preventing high aquarium ammonia: Aquarium Nitrogen Cycle and Cycling
See this article for more: Aquarium Nitrate Control

*Nitrates; under 40-50 ppm (lower yet is always better)

*GH: this is best above 100 ppm for 90% of FW fish and above 200 for over 60%

GH is also the parameter ESSENTIAL positive mineral ions (Cations) are found in, and fish kept in water with inadequate mineral cations can suffer health problems over the long term.
Wonder Shells, SeaChem Replenish, and to some degree Aragonite & crushed coral can help with important mineral cations (although crushed coral does not dissolve at a rapid enough rate to help as well)

*pH; Stable is most important, but for general community tanks a 6.8-7.8 falls within most fish tolerances as long as there is pH stability since the pH scale is logarithmic and sudden changes can be deadly.
As well, pH depends very much on the fish you are keeping. Discus prefer under a ph below 7.0, while Mbuna African cichlids prefer above 8.0, but again I want emphasize "stability" over the actual pH "number". As well KH and GH are often more important than many aquarium keepers realize (KH affects pH stability). If you manage your KH and GH levels to where they should be, your pH should fall into range. (It will not always be the same, but will be in the proper range when GH and KH are properly managed.)
Please see this article for more on the subject of pH:
“Aquarium Chemistry; pH, GH, KH”

*KH; VERY important for pH stability which is why I this is a more important test than pH in my experience and knowledge of aquarium chemistry.

Sea Chem Buffers and to some degree Aragonite can help maintain a high KH & pH when you desire an aquarium with a higher pH, KH especially where tap or well water is very acidic.
It is noteworthy that Buffers are generally best tested via KH, not pH, otherwise using buffers for exact pH maintenance can result in dangerous pH chasing.

For a lower pH in aquariums where the tap water used is very high (usually 7.8 or above), I have used blends of RO (Reverse Osmosis) water and tap water. The ratio varies with the tap water pH, KH, & GH and the water conditions I want to achieve. With Discus it can be 100% RO water assuming the water is properly re-mineralized.
Then to maintain these conditions I use peat in my filters. Another newer method for lowering pH is crushed almond husk found in Nirox Bio-Lif (instead of, or in addition to peat, to which Indian Almond Leaves are superior due to this products bacterial absorption properties). This actually works quite well for this purpose. Note that GH does not directly affect pH,
Also note that calcium is also important for fish metabolism and fish health and healing (along with other essential electrolytes/minerals found in "GH").
With the above method of using RO (or DI) water in a blend with tap water and peat, I have still been able to maintain a a low but still healthy KH and GH level.

*Caution; Soft Water Use: water that originates from a home or office water softener that uses sodium (salt) should Never be used in any aquarium.
As well use of so-called Drinking Water or 100% Reverse Osmosis water should only be used by a more advance aquarium keeper that knows how to properly re-mineral this water (for those that know how, the water quality will be top notch).
Please read why the use of Soft Water has dangerous implications for your fish:
Use of Soft Water for Aquarium; Dangers

Suggested Test Kits;
It is always best to have as many different test kits (that apply to a freshwater aquarium) as you can afford.

*Test Strips, although generally not as accurate are still very useful for quick readings that are still accurate enough (provided stored dry) for a beginner or intermediate aquarist to get a good barometer of aquatic health. The API 5 in 1 Test Strips provide 5 key aquarium parameters including the often missed KH and GH test.

For a more in depth article about Aquarium Test Kits, please follow this link: AQUARIUM TEST KITS; what they are used for and their importance.

BASIC LIGHTING:

For the average freshwater aquarium, lighting is not as important a consideration as it is for a planted freshwater aquarium or reef aquarium. However it still can make a difference on how natural your aquarium appears, as well as brown diatom algae is often a problem in established FW tanks with poor lighting (usually the incorrect spectrum, PAR %). There is also some evidence (not conclusive) that good lighting aids in Correct Redox which is a water parameter that has an definite effect on fish health.

These same 6400 K high output CFL aquarium lights can also be purchased separately and used in standard incandescent aquarium (or other) light fixtures as pictured to the left.


Another newer yet technology that is easy to adapt to a basic freshwater set up is the T2 Aquarium Light which is available in linkable fixtures for tanks from 8 to 60 gallon (or larger depending on how many are lined). The T2 would be my recommendation for freshwater aquarium keepers that want a “step up” in lighting without a high price (the T2 out perform all aquarium lamps including older technology T5 in useful light energy output for energy used except for LED).
For the highest output of useful light energy, the GroBeam LED Aquarium light is by far the leader, but this may be cost prohibitive to many basic freshwater aquarium keepers.

Finally, good ole fashioned T8 & T12 aquarium lights such as the Aquarilux by Penn Plax that are available in lengths from 12 to 48 inches are still practical for a basic FW aquarium application. Coralife, Hagen and Zoomed make comparable aquarium lights, all of which are excellent for colors of the fish, albeit lacking in lumens per output, PAR, and other lighting benefits (that are still helpful for a fish only aquarium).

I would NOT recommend standard incandescent light bulbs (which are unfortunately still sold in many aquarium supply outlets) and STRONGLY recommend the use of the CFL aquarium lights referenced above to use in these fixtures. As well, not all CFL you may see available in hardware stores, Walmart, etc are equal, the vast majority are of under 4500 K and not adequate for aquariums.
Cool White lights also are not appropriate for aquariums due to poor lumens per watt, incorrect PAR and Kelvin output which can result in growth of Cyanobacteria or Brown Diatom Algae.
Hardware Store/Walmart Grow-Light bulbs can be an inexpensive alternative and have a better PAR than most inexpensive bulbs, however even these have a low lumen per watt output and are not quite the bargain they may seem when this is considered.

Please reference this article for more about Aquarium lighting from basics to advanced (also see the basic freshwater section in the summary near the end): “AQUARIUM LIGHTING, Kelvin, Nanometers and more” .

LIVE PLANTS:

Live plants are desirable in my opinion, but many artificial plants can look quite realistic when properly arranged or used in conjunction with live plants. For a beginner, live plants are more difficult but not a lot.
The benefits of live plants are they are great at nitrate removal and keep a natural balance to the aquarium, removing CO2 and adding oxygen (only during daylight). Hornwort is an excellent plant for nitrate removal (and even ammonia removal), and is relatively easy to grow. Banana plants (when available) are also a very easy plant. Be careful with many fish that will “mow down” your plants such as: Silver Dollars, most African cichlids, and even goldfish.

For healthy plants I suggest a substrate of #00 sand mixed with SeaChem Flourite or Eco Complete about 3-5 cm deep with a layer of #3 gravel on top about 2 cm deep. This combination works well for plant roots, ease of vacuuming the top layer ONLY (where plant roots are), and for better bio filtration. You can substitute Flourite with a sandy top soil (although usually not as good a source of iron), by preparing the soil thus; Gather sandy top soil, add water with a 10/1 bleach solution, mix for a couple of minutes, then rinse (with a de-chlorinator for first rinse) until the water runs relatively clear. The sand that is left is what you mix with your plant roots, please note that although an inexpensive route to go, this ‘homemade plant substrate is not as good as Eco-Complete.

It is important to note that dying plants can add to your ammonia, nitrite, nitrate and even kH problems (production of nitric acid through decay), so is important to keep your plants healthy.

For healthy plants you will need;

*PROPER LIGHTING: 3-4 watts per gallon is quite outdated now, especially with the high end LED Aquarium Lights now available (I am not referring to the many low end LEDs such as the Marineland Double Bright, so do not make the mistake of comparing apples to oranges), as there is a lot more that goes into the equation than this. A couple are useful light energy & light spectrum/ Kelvin temperature; Photosynthesis takes place at the blue end and even more so at the red end of the Nanometer curve (420 nm blue and 670 nm red). A bulb in the 5500- 6700 K range is generally best for plants. The Lux that reaches the plants is also important.
For a more in depth article about lighting please see: “AQUARIUM LIGHTING, Kelvin, Nanometers and more”

*SUBSTRATE for a healthy root structure;
This is provided by a good sandy base and careful cleaning so as to not disturb this. The roots are support symbiotic bacteria that aid in Nitrate assimilation and other processes.

*BIO AVAILABLE CARBON and a Proper gas exchange:
Good surface agitation where gasses such as Oxygen and CO2 are added/ subtracted from the aquarium. You can add to the bio available carbon and CO2 levels through a product called Sea Chem Flourish Excel , a CO2 generator, or by powdering some Ammo Carb (for carbon and Iron) into a fine powder and gently adding this with finger tips around the plants. (The first two methods are more effective)
This is where there is a lot of misunderstanding, the key is bio available. This why I find the Flourish Excel a useful albeit basic product as this is bio-available organic carbon.

*PROPER NUTRIENTS OR ‘FERTS’:
You will need a Nitrate level between 15-40 ppm, iron (best in the soil, which is where the laterite helps), LOW phosphate levels to help plants compete better with algae, and many other trace elements that should be present from fish waste with a proper feeding regimen.

Some Plants to Have:

• Hornwort (Ceratophyllum demerson)
• Java Moss (Vesicularia dubyana)
• Dwarf Anubias (Anubias nana)
• Java Fern (Microsorum pteropus)
• Water Sprite (Ceratopteris thalictroides)

FOR MY FULL PLANT ARTICLE, please follow this link: Aquarium Plants; Substrate, Ferts, CO2, Lighting, and other Factors

FISH ACCLIMATION:

Once you have removed your chlorine (if necessary) adjusted your temperature, checked basic water parameters (kH, pH, Ammonia), you can start with a few fish. It is best to wait at least 1-2 days for the first fish after initial set-up. Float the bag your new fish came in for 10 minutes, then open the bag and add a small amount of water. After 5 more minutes add some more water, and continue this process for about 30 minutes. After 30 minutes, gently remove your fish without adding ANY of the bag water to your aquarium to prevent disease transfer.
Also see this article:
Aquarium Disease Prevention; Acclimation