Treating Cotton Mouth (A strain of Columnaris)

Treating Cotton Mouth (A strain of Columnaris)

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In this article I will discuss Cotton Mouth which is a certain strain of columnaris. Some treatments recommended in this article may work for other strains of columnaris but this article is still specifically for cotton mouth.

Important Reminders
  • This disease is very contagious, act fast
  • Best results occur when all non-medical treatments that are suggested in this article are used together.
  • Tetracyline, melafix, etc. is completely useless be very careful with what you are buying to treat your fish in most cases it just won't work. Minocyline in maracyn 2 is like tetracyline. Tetracyline is not very effective against the bacteria unlike maracyn 2. I'm not sure why this is but Tetracyline has proven to be not as effective.
Cotton mouth can also be called; mouth fungus, mouth rot and live bearers disease.

Symptoms and Identification
Cotton Mouth can be identified by a white growth on the mouth of a fish. The growth will start as a small white bump.


Cotton Mouth is caused by stress, if a fish is stressed it will weaken its immune system therefore making it susceptible to diseases so if you can prevent stress you can optimise your chance for a recovery. It is rare that your fish will develop this disease from your aquarium it is mostly commonly added to aquariums from new fish which have been in transit and changing environments. Injury can also cause the bacteria to take hold of the fish. Columanaris is always present in the aquaria but can only take hold of a host when the fish is injured and/or has a weakened immune system.

Remove or prevent fish stressors such as temperature and parameter fluctuations or aggressive fish.

The Disease
Columnaris in general is an aerobic negative gram bacterial disease it is not fungal as it is usually mistaken for. Columnaris is present in your aquarium at all times yet only affects fish when stressed. It takes advantages of the weaken immune system and uses the stressed fish as a host. All strains of columnaris are fast spreading and contagious. Cotton mouth is a very slow killing disease it could take up to a year before acting killing its host. It does not start to affect fish's quality of life until the late stages of the disease where the growth may be so large the fish cannot shut its mouth of open it too feed. The fish will usually be killed by the disease from starvation in one of two ways; the bottom half of the mouth will fall off or the fish will be unable to consume food. Cotton mouth will continue to stress the fish out and can cause the fish to develop more illnesses such as fin rot, bent spine, etc.

Non-medical Treatments
There a few things that can be done in order to slow the disease and aid in destroying it.

1. Move to a quarantine tank, (with fish that have not yet been added to the tank) this is a very important step ill fish will pass the disease on to other fish, the disease needs to be isolated in order to stop the wiping out of your stock. By doing this you will also be able to easily track progress of the fish and prevent stress to unaffected fish as a result of treatments. If an outbreak occurs in a tank but not all fish seem affected treat the whole tank anyway as the disease is likely hosting in other fish but it is not yet visual.

2. Lower the temperature of the water, this bacteria can multiply more rapidly in higher water temperatures. There are many aquarists that raise the temperature of the water in order to try and kill the bacteria but end up hastening the demise of their fish. 74F (23C) is ideal.

3. Add Aquarium salt, you must use the largest amount possible which is one generous table spoon per 5 gallons. Our filtered tap water contains very little salt, there is usually a trace of salt in a native fish's environment so fish sensitive to salt such as corydoras can tolerate a tad of the stuff. Salt is really important for treating columnaris because firstly it acts as an antiseptic, it inhibits further reproduction of columnaris to an extent. Salt is also important because the disease messes with the gill function of the fish by adding salt you improve gill function but also slow osmoregulation which can help the fish's immune system deal with the disease. You are basically dehydrating the bacteria to death, you could do this with a fish if you added enough salt too. Salt also helps in disease control because the fish is stressed with this growth on its mouth it is susceptible to more disease. Columnaris is also not found in saltwater fish because it cannot live in salt water.

You need to do these things if you want any hope in treating the disease any antibiotic will be useless these things are done. Columnaris also likes to live in detritus when without a host, a gravel vacuum can reduce the amount of the bacteria in your tank.

Treatment in the USA
Luckily for the US there are a wide variety of easily available treatments.

  • Maracyn 2*, treats a wide range of bacterial diseases that are gram negative perfect for cotton mouth. Maracyn 2 is not as rough as other treatment are for your fish.
  • Kanaplex*, is a tougher treatment for your fish but has proven very successful
  • Furan-2, this treatment has also proven rather successful
  • Medicated food such as Jungle Anti-Bacteria or GelTek Ampicillin greatly improves the chances of survival
Kanaplex and Maracyn 2 in conjuction has proven to have very good results.

Treatment in Australia
  • Tri-Sulfa, is readily available in your local pet barn, etc. this medication only makes the disease from progressing (bacteriostatic). I would suggest using this while waiting for other treatments to arrive. Each treatment lasts for three days, dissolve a tablet for every 10g in a cup of aquarium water before adding to the tank. After every three days I like to do a water change and then add another full tablet. This treatment only prevents the bacteria from continuing to multiply. The treatment alone will not cure the disease.

Microbe-lift Gram Negative / Gram Positive (linked below) contains nitrofurazone as does Furan-2. I tried both these medications and they both failed. I found a two conclusions;
  1. the disease had processed too much for the medication to be effective

2. the medication is only successful when used in conjunction with other medications such as Kanaplex​

Because of Australia's tight restrictions on various chemicals and substances entering the country I find it virtually impossible to cure the disease.

The products are linked below:
Microbelift Gram Negative/Gram Positive.
Furan 2

My effected fish died from the disease, if I were to experience the disease again the effected fish would be euthanized as I have found that in the both cases I have had the disease the fish have always died and that there is no cure.


Any other methods that you know work to treat this disease would help improve this article. Please comment them below
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very good review, the only thing i would change is saying that salt will harm some fish more than do good, because they are so sensitive.
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