FLEXIBACTER- COLUMNARIS & FUNGUS (Saprolegnia):
The Proper Treatment, Identification, & Prevention of the Gram Negative Aerobic Bacterium Columnaris & Fungal Infections
WHAT IS COLUMNARIS?
Columnaris (often referred to in the past as "cotton wool disease" or "cotton mouth disease") is a warm water, gram negative strictly aerobic and nonhalophilic (meaning they do not live in saltwater conditions) bacterium often appears like a fungus (or more correctly; Saprolegnia) however it is not a fungus, although many treatments for fungus are effective for mild cases of Columnaris (Flexibacteria).
Identification (& Causes)
• A white spot/wound in the body maybe 3/16 inch, that within a week the white area increases to a larger strip in size.
• In gills, Columnaris can cause disintegration of the gill filaments. As the disease progresses the gills can change from their natural color to a light or dark brown. Since it is difficult to absorb enough oxygen from the water using damaged gills, the fish will start breathing rapidly and the fish might also swim up to the surface gasping for air.
• A white to grey cottony growth (that appears like a fungus) but it appears to be eating away the fish’ skin, as well appears the outside skin is eaten away down to the 'meat'.
(The picture to the left shows necrosis of the fins, please click the picture to enlarge)
• Necrosis (premature death of cells and living tissue) of the fins which is accompanied by white, cotton-like accumulations of bacteria and detritus. Fin Rot is a common secondary problem of Columnaris (see the picture in the treatment section)
(See the picture to the left)
• Ulcerations on the skin that slowly or sometimes quickly result in major tissue (epidermis) loss.
• Sometimes the infection where Columnaris is present is a blackish to fleshy in color.
• A lesion that appears like a white/grey “Saddleback” near the dorsal fin (which leads to the other common name for this disease: “Saddleback Disease”.
As well the skin lesions will often appear white/gray colored with an edging of red, which will often change to ulcers caused by the bacteria decaying the underlying tissue.
(The picture to the left shows white/gray fungus "like" skin lesions, please click the picture to enlarge)
• Occasionally Columnaris can appear as a mouth "fungus", however this may actually be Saprolegnia or even Streptococcus
• IMPORTANT; often Columnaris infections are present in well circulated, oxygenated tanks, unlike Aeromonas Infections which are often anaerobic and are much more common in tanks with poor circulation, high bio loads, and large amounts of organic wastes.
The bottom line is Columnaris is an aerobic bacterial pathogen that does NOT thrive on organic wastes (this despite claims of inaccurate, poorly researched articles about Columnaris such as one found at about.com!!).
I want to make clear, since many web sites note that Columnaris is generally found in tanks with poor water quality, that this is an incorrect way to diagnose Columnaris (barring a microscopic slide) since this pathogen is aerobic and can become pathogenic in otherwise well maintained tanks (as per many measures of water quality), yet has other stressors that allow for a Columnaris infection such as injury from harassment.
In fact since Columnaris is strictly aerobic, the addition of more aeration/circulation will do nothing to stop Columnaris other than to possibly help the fish fight this disease pathogen.
Unfortunately this key point is so often missed, as this totally incorrect statement from a popular web site shows:
“Columnaris reproduces poorly in the presence of oxygen in the water, so keeping the water's oxygen content up by creating a current can help prevent Columnaris” WRONG!
Columnaris often results in wounds when stress is common in an aquarium or from handling, shipping or any other stress inducing factor for fish.
So a diagnosis of a growing sore as Columnaris in a tank that has fish that are under constant harassment by other fish is often a correct assumption (common in many Lake Malawi Mbuna fish in injuries incurred).
• Sores, wounds, or infections that grow even while under treatment of gram positive medications such as Melafix or Erythromycin may be an indicator of a Columnaris infection as well. Unfortunately Maracyn (which is Erythromycin) is incorrectly prescribed to treat Columnaris by many that do not know that Columnaris is gram negative bacterium while Erythromycin is a gram positive antibiotic.
• Temperature Spikes or sustained high temperatures can often allow for a Columnaris infection to take hold in an otherwise healthy aquarium especially if other stressors are present such as injury, stress, age, etc. (in fact sudden increases in temperature is a common cause of a Columnaris outbreak in an aquarium or pond).
Columnaris thrives in temperatures above 80 F (I have observed 85-90 to be a range where Columnaris is most virulent). A temperature in the 80s is more a factor in cold water fish such as Goldfish.
• Finally, since Columnaris is an opportunistic aerobic infection even a well maintained aquarium can suffer from a Columnaris infection with even a slight opportunity for infection (assuming this bacterial pathogen is present). A common portal for a Columnaris infection is simply an older and weaker fish. Old age allows many opportunistic infections to get a foothold in at least the fish in question.
This is important to note, since treating a fish that has his/her immunity and normal body functions in decline may often be futile. This does not mean it is not worth while attempting a cure, only that an aquarium keeper should not beat him or herself up over failure to cure a favorite fish that has been well cared for since bringing the fish home. I have seen this with Bettas in particular over the years since these popular and personable fish often win us over in our hearts, but have a short lifespan even with the best of care (this lifespan can vary depending upon whether kept in an aquarium or bowl).
Treatment Information:Besides the obvious first step of lowering stressors and improving water quality, additional salt is helpful too at a dose of 1 tablespoon per 5 gallons OR HIGHER.
In fact a study at the Alabama Agricultural Experimental Station, Auburn University has shown increasing salt concentrations used with Channel catfish (along with heat reduction to 75 F) can treat Columnaris (Flexibacter) infections. This study flies in the face of anecdotal advice about not using salt with catfish.
See the chart to the above/left for the mortality rate of Catfish with Edwardsiella ictaluri (which is a similar gram negative rod bacteria to Columnaris) treated with salt at different levels, please click to enlarge.
You can see from the diagram that the best results were achieved at a dose of 3000 milligrams per liter; based on the weight of salt this converts .67 teaspoons per liter or 2.54 teaspoons per gallon. This is Much more salt than many aquarists commonly believe a Catfish can tolerate.
Please keep in mind that this amount of salt is NOT meant for long term use, rather just the duration of time it takes to reach a cure for the Columnaris infection.
This amount of salt is most simply used in a 30 minute bath, however as per this study it can be used in the main display aquarium/tank. If added to the main aquarium, I recommend building up to high level suggested by this study over a 2 day period.
A Fish dip or bath in Mebromin, Potassium Permanganate , Methylene Blue (not to be confused with malachite green) has also helped speed cure in most instances for my clients fish (or my personal fish) and SHOULD BE part of most Columnaris Treatment regimens!
In fact with many instances of Columnaris the Methylene Blue Bath (or the even more strong, but more carefully administered Potassium Permanganate bath) was the main factor of treatment that affected a cure as per many tests.
See the picture above/left for a Betta also displaying secondary Fin Rot that literally was on "deaths door" (laying on the bottom with little response) that recovered with a treatment regimen of Kanamycin & Salt as well as regular fish baths which included Methylene Blue, Salt, and Kanamycin.
Please click to enlarge.
The Bottom line is a Fish Bath and maybe a swab too is a MUST part of any moderate to serious Columnaris infection treatment!
With Methylene Blue or Potassium Permanganate I prepare a double strength bath and place the fish in this solution for 30 minutes).
I strongly recommend this bath as a FIRST course of action.
Furan Two and/or Kanamycin can be added to this 20-30 minute bath for more serious or stubborn cases, HOWEVER do not combine these medications or any others with Potassium Permanganate.
Please see this article for more about Baths:
“Fish Baths, Dips, Direct Treatment Applications”
As well as the above noted baths, direct applications of Methylene Blue, Hydrogen Peroxide or Diluted Potassium Permanganate to external areas of infection can help with recovery and may be your only chance to check the spread of a more serious infection of Columnaris.
Many fish diseases, it should be noted, are caused by different bacterial or fungal pathogens that often exhibit similar symptoms, so identification of a specific bacterial or fungal pathogen is not often possible from mere visual inspection of the symptoms on the fish.
By using broad-spectrum treatments such as a Furan Two & Kanamycin combination against diseases with similar symptoms affecting fish, precise identification of specific bacterial or fungal pathogens causing the disease that often display similar symptoms may not be absolutely necessary.
Triple Sulfa may also yield positive results for treatment of Columnaris if used early (although this is not as effective of a treatment for Columnaris as it used to be or as the Kanamycin/Nitrofurazone combination).
My professional use of Triple Sulfa has found that it is a good choice along with baths and some salt for mild to moderate infections and is rarely harsh on aquarium environments including plants.
Pimafix can aid as a natural treatment for MILD cases of Flexibacteria (I would NOT recommend it for more serious cases). Do not confuse Melafix with Pimafix, as Melafix is more of an antiseptic with no effect on Columnaris whatsoever!
Pimafix is effective for a broad range of mild bacterial and fungal infections that typically afflict fish and other aquatic animals (especially gram negative). Fish diseases that may be treated in accordance with this product include bacterial fish diseases, such as fin and tail rot, mouth fungus (often caused by the bacterium Flavobacterium Columnaris); fungal fish diseases (such as those caused by microorganisms of the genera Saprolegnia and Achyle) and the like.
Unfortunately, there is much unfortunately posted in forums or websites about the use of Tetracycline or Oxytetracyline for the treatment of Columnaris however this is based on old research and misunderstanding of the large Tetracycline class of medications.
Tetracycline is primarily gram positive while Columnaris is a gram negative rod bacteria (although Oxytetracycline is more broad spectrum than Tetracyline Hydrochloride, it is still primarily a gram positive treatment).
This said Minocycline is member of this class of Tetracycline antibiotics and many persons assume all antibiotics in this class are the same, which is not true. Minocycline (sometimes spelled Minocycline) is more gram negative than its cousins and has shown effectiveness for Columnaris.
Maracyn 2 is a product that contains Minocycline.
That said, the Tetracyline family of antibiotics should never be your first choice of medication treatment, despite some misinformed information stating otherwise (please note that I make this statement based on researched medication facts as well as MUCH practical experience dating back to 1979).
Additional or Follow-Up Treatments;
Among other treatments I have used, especially to prevent reoccurrence once the fish are OK are “Medicated Wonder Shells”, which contain Acriflavin (as well they contain Methylene Blue). Acriflavin is active against flex bacteria in mild cases.
While I do NOT recommend Medicated Wonder Shells for a full blown infection of Columnaris these can be an excellent follow up treatment about 7-10 days after completion of regular treatment and baths. These are helpful in part for a Columnaris infection due to the positive mineral ions they deliver along with medication.
I do suggest a water change and adding carbon to filters prior to the introduction of a Medicated Wonder Shell, or other follow up treatment.
FINALLY, in summary of treatments; one aspect I found over and over, including when I have compared notes with other aquarium maintenance professionals is that attempting to mix a little of one method of treatment with another almost always results in failure.
In other words, if you have found a treatment you have found that works that differs from what I have stated, GREAT!
But do NOT attempt to mix what is suggested here by leaving out some aspects of these treatment steps (or another methods) and expect success. Also as I have already noted, do NOT leave out the importance of correct water parameters, in particular positive mineral ions play in the success of a Columnaris treatment regimen.
PREVENTION & FURTHER COLUMNARIS (Flexibacter) INFORMATION:Flavobacterium columnare gained the nick name “Columnaris” because wet mounts of Flexibacter prepared from diseased fish appear as column-like, "haystack" colonies.
Columnaris, which is a gram negative aerobic bacterium, is often prevalent in systems with poor mineralization.
See this article: “Importance of Calcium, Electrolytes and more in Aquariums”.
As well; crowded conditions (often in re-circulating systems), aggressive inhabitants, poor handling, poor Redox Balance, sudden temperature spikes (or prolonged temperatures much above 80F), and the stress from high bio loads are all conditions that can allow for an opportunistic Columnaris infection.
Please note; high bio loads is more symptomatic of Aeromonas or Saprolegnia infections.
Columnaris bacterium have caused problems for fish farmers for many years. It is not easy to control, and because the disease is related to stress, an effort to identify and correct the source of the problem is necessary to prevent excessive or chronic mortalities.
Fish are particularly vulnerable to Columnaris following handling and transport, especially since Columnaris is opportunistic warm water pathogen that is often always present in the water, it simply needs an “opportunity” to become pathogenic.
Abrasion from nets, transport, crowding, aggression by tank mates, and adverse water quality conditions (such as lack of necessary electrolytes/minerals) create a situation which is very conducive to Columnaris outbreaks.
With this in mind; lowering stress (such as removing an aggressive inhabitant), improving minerals/electrolytes, and keeping a clean well filtered aquarium are first steps in treating or preventing Columnaris.
Parameters to Consider for Prevention and Treatment of Columnaris:
Please note that if ANY of these parameters are "off", it may difficult or even impossible to effectively cure a serious Columnaris infection!
*Decrease Fish Load, Crowding Columnaris outbreaks have been shown in University studies to be prevalent in crowded, re-circulating systems, which is a reason I recommend against these types of systems even for fish stores.
This is also common in “African Cichlid” tanks or similar where there is constant stress due to constant battling for hierarchy.
*Ammonia, nitrites; should be 0 ppm
*Nitrates (long term exposure of nitrates over 80 ppm can reduce resistance to disease, under 40 is better)
*Lower your temperature; under 75 F (24 C) (only during treatment).
Goldfish and similar cooler water fish should always be kept under 80F (27C) whenever possible.
*pH (depending upon fish kept) Stability is more important than the actual pH. In other words, do NOT chase you pH, find a KH above 50 ppm and keep your pH stable at whatever pH you get, whether 6.5 or 7.5
* KH: generally a KH of 50 + (what is best here depends upon fish kept). This is related to pH and maintains pH stability via adequate carbonates
*Positive Ionic Composition of the Water & GH: this is a little more complex than this article will deal with, however this is related to both the GH and Redox. In a nutshell MG++ (positive magnesium ions) and CA++ (positive calcium ions) play a part in adhesion of Columnaris by reducing surface potential and repulsive forces. This is important, please read this article for further information:
Aquarium Chemistry; GH, Calcium, Magnesium, Positive Mineral Ions/Cations.
*Redox Balance; although not generally a major concern for the average aquarist, it is important to understand when problems persist especially since newer research shows its importance in disease prevention. This is an important consideration for an aerobic bacterium such as Columnaris, since often other more obvious water parameters may be good while this one is not.
Redox balance is related to GH (although if all positively charges ions are lost from calcium and other minerals that make up GH, you can still have a higher GH of say 300 ppm and still have a poor Redox Balance).
But the point I want to make is that websites such as Wikipedia and many others are dead wrong to imply that "The bacteria can persist in water for up to 32 days when the hardness is 50 ppm or more" is a causative factor for Columnaris.
While Columnaris Bacterium certainly need these minerals, so do fish and to make the strange leap of thought to state any GH over 50 can lead to Columnaris. This is simply bad science, not to mention proves a lack of practical experience on the part of authors of these articles.
The fact is 50 ppm is a very low GH, even for many soft water fish and more importantly these minerals are essential for correct osmoregulation and a supplier of essential positive electrolytes necessary for fish immunity that Redox research has proven. It is noteworthy that these mineral cations play an important role in adhesion of Columnaris by reducing surface potential and repulsive forces, so for an aquarium keeper to attempt to lower minerals and positive mineral ions is misguided at best.
*Consider ALL steps outlined in this article: “A Healthy Aquarium; Disease Prevention”.
The more steps you follow in this article, ESPECIALLY the use of a TRUE UV Sterilizer, the lower your chance of opportunistic disease outbreaks such as Columnaris (or Saprolegnia/Fungus).
Unfortunately what passes for a UV Sterilizer lately (for under $50) is nothing more than a clarifier and will provide NO aid to the prevention of Columnaris whether directly or as a major aid to a healthy Redox Balance
Please read: UV-C Sterilization; Facts & Information
For the previous stated water parameters, water changes are often very helpful (although watch cross contamination if you have more than one aquarium).
*Good filtration (two filters is always a good option), is very important for treatment and prevention. It is important to catch this disease early, as Flexibacter advances it attacks the internal organs making for more difficult treatment. Kanamycin is about the only antibiotic that will work at this time (unless you have access to Chloramphenicol).
This said, circulation and dissolved oxygen do not play as big a role as with the diseases Aeromonas, Furunculosis, or Vibrio, since Columnaris is a aerobic bacterium that needs oxygen while these others are anaerobic meaning they do best in environments without oxygen.
Please note that Anabantids (such as Gourami and bettas) seem to be especially susceptible to this disease, which is good reason to practice good cleaning practices with these fish even though they have the ability to get oxygen from the air. Wonder Shells are great to use in Betta bowls as they add needed electrolytes and calcium and improve water quality between cleanings.
*Genetically Weak Fish, often over breeding or exposure to poor conditions such as with "feeder goldfish" can set up a fish for an opportunistic Columnaris infection. Sadly with genetically weak fish or fish exposed to poor conditions that permanently damage internal organs often NEVER recover from Columnaris, even with the best efforts.
From my experience and speaking with others in my profession, Crown Tail Bettas seem to be especially susceptible to fatal Columnaris infections.
For further reading about Columnaris, please read these outside resources/references:
*Prevalence of Edwardsiella ictaluri and Flavobacterium columnaris
*“Influence of water quality and temperature on adhesion of high and low virulence Flavobacterium columnare strains to isolated gill arches”, Decostere, A., Haesebrouck, F., Turnbull, J. F., (1999), Journal of Fish Diseases, 22:1; 1 – 12
Section Two: SAPROLEGNIA (Fungus):Saprolegnia (often classified as a mold; from the Genus “Saprolegnia”) is often confused with Columnaris and for good reasons, they can often be similar in appearance.
Close inspection though will reveal that a fish with Saprolegnia will have hair like growth structures similar to what you might find outside growing on a decaying piece of wood in the forest. This is what differentiates Saprolegnia (fungus) from Columnaris as you will not see the thin hair like structures upon fish with Columnaris.
(Please click picture to enlarge)
Another consideration in differentiating Fungus (Saprolegnia) from Columnaris is that Saprolegnia & fungi often grow on dead tissue, unlike Columnaris which must having living tissue to live on. This is an important distinction, since it is often dead if found on dying or dead tissue of a live fish, as well as the remains of a decomposing fish, shrimp, etc.
One more consideration for the identification of Saprolegnia/fungi is that out breaks often occur in aquarium/pond with large amounts of decaying organic matter, with low pH and poor circulation in the area of decay.
Saprolegnia is not a true fungus (fungus are from the Kingdom “Fungi”), while Saprolegnia are from the Kingdom “Protoctista” which is a catch all Kingdom for the multicellular organisms which don't fit into the Animal, Plant, or Fungus Kingdom. This includes molds, green algae, red algae and more. Oomycetes.
Please Read Reference #1 at the end of this article, as this is an important definition that so many aquarium website information articles on this subject get wrong such as one found at FishLore.
These organisms, considered to be saprophytic "water molds," are a normal, ubiquitous component of aquatic ecosystems (Saprolegnia are present in ALL aquariums and ponds). Saprophytes live off of decaying organic material.
If you have ever seen a piece of fish food left in the aquarium and was covered in what looks like cotton, those are all fungus filaments doing their job of breaking down organics, and although they are a natural part of the aquatic environment, an overabundance of Saprolegnia (Fungus) caused by decaying matter (especially in new aquariums) can result with the Saprolegnia to start trying to break down your living fish and can also appear as cottony growths on the fish as well.
The picture to the left is a double close-up of a fish tail with Saprolegnia/Fungus, with inner picture a multiple magnification of how the Saprolegnia “mold” looks
Saprolegnia will often get started if there is a large amount of decomposition of nitrogenous organic material such as dead fish left in the aquarium or large amounts of high protein fish food such as krill/shrimp. Injured fish with open sores will amplify this potential problem. This is why I generally recommend against using raw shrimp cycling method recently re-popularized on the internet by a few websites and some forums such as Yahoo answers and that is to use raw shrimp to seed the nitrogen cycle as this can result (as per my own studies) in Saprolegnia getting to strong a hold in a new aquarium (please read further about the lifecycle of Saprolegnia zoospores to also explain the risks, as well as the references).
TreatmentLuckily treatment is somewhat related to Columnaris (which Saprolegnia is often confused with unless view microscopically then the difference is clear), although Saprolegnia responds well to these chemical (as well as a few antibiotic/organic remedies):
*Acriflavin (found in API Fungus Cure) for mild to moderate Saprolegnia infections
*Oxidizers such as Potassium Permanganate or stabilized oxygen chlorine (Maroxy).
*I recommend in most moderate to severe Saprolegnia/fungus infections a Medicated Bath using Methylene Blue OR Potassium Permanganate (not mixed). Methylene Blue can be combined with Nitrofurazone (Furan 2) for increased effectiveness.
Potassium Permanganate can also be used as a swab in mild isolated cases of Saprolegnia/Fungus then as a bath for serious cases. This bath can also be helpful even in mild cases to increase the chances of success of many mild to moderate treatments such as Pimafix or Kordon Rid Fungus).
Please read this article for more about fish baths: Fish Baths, Swabs, Dips
*Malachite Green based treatments such as Medicated Wonder Shells, ParaGuard or Quick Cure .
*Organic Remedies such as Pimafix or Kordon Herbal Ich Attack (AKA Rid Fungus) are often successful in mild to moderate infections.
*Antimicrobials such as Triple Sulfa also works reasonably well for Saprolegnia (fish fungus).
*For very difficult cases of Saprolegnia (especially when parasites are also suspected/involved), a strong cocktail of SeaChem ParaGuard (or Quick Cure) and Furan 2 OR Triple Sulfa may prove successful.
Please note that many of the above remedies can be combined for more strength, however others cannot, such as the oxidizers (Potassium Permanganate or stabilized oxygen chlorine).
Medicated Wonder Shells have several ingredients combined (Malachite Green and Acriflavin to name two) but is not as strong for serious fungus/Saprolegnia outbreaks (since these are not combined at full strength in Med. Wonder Shells) as combining other full treatments such as ParaGuard and Triple Sulfa or Acriflavin.
Salt, dips, and baths are also effective (in serious cases essential) as part of a Saprolegnia treatment. I would use plain salt (non iodized) or better; ”SeaChem Cichlid Salt” which is a balanced salt with other essential elements necessary for most freshwater fish (not just cichlids as the name implies).
As noted earlier, a Methylene Blue or Potassium Permanganate bath used at double tank strength for 30 minutes twice per day with the bath water disposed of afterwards is also very useful for Saprolegnia (Fungus) treatment (generally Potassium Permanganate is more effective for Saprolegnia).
However treatments often useful for Columnaris such as Kanacyn are less effective for Saprolegnia/Fungus.
This said, I disagree with some statements I have read about the use of antibiotics for Saprolegnia stating that these should not be used over concern for the nitrifying bacteria; these statements are based on gram positive bacteria such as Erythromycin which can and will harm your nitrifying bacteria, however the antibiotics which are effective for Saprolegnia and Columnaris are gram negative and would take over use to destroy you bio filter bed.
As for Erythromycin, I have read many fish keeping articles (especially on Betta forums) where Erythromyin (aka Maracyn) is recommended for Fungus (Saprolegnia); This is simply WRONG! While Fungus is not a bacteria and so cannot be labeled as either gram positive or gram negative; the fact is gram positive medications do not treat true fungal/saprolegnia infections and even if this is a misdiagnosis with Columnaris, this is still incorrect since Columnaris is gram negative. Sadly this misformation is cut and paste around resulting in many needless fish deaths based on my experience and emails!!
Saprolegnia (fungus) can be even more opportunistic in poor water with stressed or injured fish than many bacterial infections such as Columnaris, so healthy water conditions are even more important for cure (& prevention) and if water conditions are poor, all the medications in world may not affect a cure!
The obvious 0 ammonia/nitrites are important but so is the often forgotten GH and a stable pH (provided by a proper KH). Without adequate calcium (found in GH) your cure will be difficult to achieve. Medicated or regular Wonder Shells may help in this area.
Also important is a clean tank without organic mulm buildup, so make sure there is NO decomposing organic debris which can by itself bring on a Saprolegnia infection, in fact I have documented this which is why I generally recommend against using raw shrimp to start your nitrogen cycle.
Please see this well researched article for more about the Aquarium Nitrogen Cycle: “The Aquarium (& pond) Nitrogen Cycle”.
This article about aquarium cleaning may also be useful: “Aquarium Cleaning”
Prevention/Lifecycle of SaprolegniaUnderstanding the lifecycle and Prevention of Saprolegnia is probably the best “cure”.
The lifecycle is best described this was: the asexual spore of Saprolegnia release motile, primary zoospores.
These primary zoospores are active only for a few minutes before they encyst, germinate, and release a secondary zoospore.
Secondary zoospores are more motile for a longer period of time than primary zoospores and as well are considered the main dispersion phase of Saprolegnia.
The repeated cycles of encystment and release, called "polyplanetism", allows secondary zoospores to make several attempts to locate a suitable substrate or host.
It is these Secondary zoospores which are considered the infectious spore of Saprolegnia and can reside in grave/substrate, filters, and the water column for some time until this host is found (these spores do NOT require a food source during this time as well). Repeated vacuumings and large water changes can reduce this number but not totally alleviate it unless the tank is sterilized with bleach (especially since these spores can reside anywhere in an aquarium), so denying the zoospores a host via healthy, non stressed disease resistance fish is the next step.
This is major reason why the long ago discredited "Raw Shrimp" aquarium cycling method should NOT be used!
Please click on the diagram for a better view/larger diagram of the Saprolegnia lifecycle. (from http://hmsc.oregonstate.edu/classes/MB492/saprokent/saprolegnia.htm )
Make sure to vacuum out ALL decaying organic matter, especially high protein organics such as uneaten shrimp or similar. I recommend treating all wounds in fish immediately when discovered, slowly increasing pH (for fish that can tolerate a higher pH, which even Discus can thrive/breed in a pH above 7.0) and finally maintain proper electrolytes (such as calcium) in your aquarium as well as the possible addition of salt when wounds are discovered for healthy osmoregulation.
It is noteworthy that Saprolegnia thrive in lower pH water, especially under 6.0, although any water under 7.2 provides a habitat that can support strong Saprolegnia growth. With this in mind, keeping slightly more alkaline water is both good treatment and prevention for Saprolegnia.
As to correct levels of electrolytes such as calcium (which is all too often missed by many anecdotal aquarium articles) is that CORRECT mineralization induces a healthy mucous layer on the fish epidermis which is so VERY important in fish resistance to Saprolegnia infections, in fact this quote from Oregon Sate University says it best:
“Willoughby (1989) determined that fish have 3 types of defenses against Saprolegnia. *First, the physical removal of attached spores by the renewal of mucous.
*Second, a morphogen in the mucous inhibited the growth of mycelium but not killing it. *And third, a cellular response in the mucous is directed at growing mycelium.
Therefore, the mucous acts as a primary physical barrier (Bruno and Wood, 1999; Pickering, 1994), by continuous replenishment of the mucous layer (Pickering and Willoughby, 1982), although not for complete, i.e., 100%, removal of fungal spores (Murphy, 1981; Willoughby and Pickering, 1977).
However, a fish having an intact epidermis is probably the best defense against saprolegniasis (Hatai and Hoshiai, 1994; Pickering, 1994).”
Please follow this link for more from the article from which this quote came: “Saprolegnia; There’s a Fungus among us” .
This why I cannot emphasize more the need for correct mineralization (products such as Wonder Shells are excellent for this), the use of salt when needed, possibly a higher pH or KH and over all good water quality that includes a healthy Redox Balance.
See also Aquarium/Pond Chemistry
As with Columnaris, the use of a correctly set up, well designed UV Sterilizer (such as the Premium TMC Vecton or Advantage UV Sterilizer) can help with Saprolegnia (Fungus) prevention.
See: UV Sterilization; Facts & Information
For further reading about Saprolegnia, please read these outside resources:
(1) " Kingdom Protoctista is defined by exclusion: its members are neither animals (which develop from a blastula), plants (which develop from an embryo), fungi (which lack undulipodia and develop from spores), nor prokaryotes. They comprise the eukaryotic microorganisms and their immediate descendants: all nucleated algae (including the sea-weeds), undulipodiated (flagellated) water molds, the slime molds and slime nets, and the protozoa. Protoctist cells have nuclei and other characteristically eukaryotic properties; most have aerobiosis and respiration in mitochondria and 9+2 undulipodia at some stage of the life cycle."
(2) “What is Saprolegnia? By Kent Mayer OSU Department of Fisheries and Wildlife” ,
(3) “Fungal Diseases of Fish”
(4) Neish, G.A., and Hughes, G.C. 1980. Diseases of fishes, Book 6, Fungal Diseases of Fishes. T.W.F. Publications, Neptune, New Jersey. 159 p.
(5) “The Occurrence of Watermolds with respect of pH of Water ”
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