I wanted to do an article on one of the other common fish diseases. I hope this will help us to be more well informed and able to see the early signs of this disease. Several of the resources I listed have photos of what the fish with Columnaris looks like. I did not have permission to use the photos so I didn’t list any.

Disease Type: Bacterial (gram negative rods)
Organism: Flexibacter Columnaris
Names: Columnaris, Cotton-Wool, Cotton-Mouth, Flexibacter, Mouth Fungus
-White spots on mouth, edges of scales, and fins
– Cottony growth that eats away at the mouth.
-White “pimples” around the chin and mouth area
-Fins disintegrate beginning at the edges
-‘Saddleback’ lesion near the dorsal fin
-Fungus often invades the affected skin
-Clear stringy feces and loss of appetite

Commonly attacks live bearing fish, labyrinth fish and catfish, but can infect any fish. Columnaris bacteria usually attaches itself to a fishes head, mouth, or lips. This disease can be mistaken for a fungus infection because of its moldy appearance that looks like cotton. . Upon close examination of the “cottony” patch a true fungus has hairy looking strings that come out from the patch and Columnaris has a fuzzy or linty appearance. Most infections are external and appear as a white or grey spot on the head. As the disease progresses the spots may turn yellowish or brownish or have a red tint. Columnaris bacteria enter through the mouth gills or skin wound. Columnaris is extremely contagious and can be spread by food, nets and containers from one tank to another Lesions on the back usually look like a saddle and can progress until the underlying muscle tissue is exposed. lesions on the mouth will look moldy or eaten away which is why it is often mistaken for mouth rot. Fins may also erode or fray and the gill filaments will deteriorate and the fish may begin panting. In acute cases the disease spreads very quickly and can kill entire tank populations in a matter of hours. temperature seems to have some affect on the mortality rate of the fish. Temperatures of over 54 degrees Fahrenheit have shown a higher mortality rate. you cannot prevent Columnaris by lowering temperature or help treat the disease by lowering the temperature. Coldwater fish are also affected by Columnaris in temperatures lower then 54 but have a slightly lower mortality rate. There is an incubation period of 24hours to 14 days, therefore a quarantine period of 2 weeks should be sufficient to rule out the appearance of the disease.

Treatment: Fish in a community tank should be removed and treated separately in a hospital tank. Closely observe the remaining occupants of your aquarium. Do a good water change, including vacuuming the gravel, add aquarium salt if the fish will tolerate it. Treat with copper sulfate malachite green) or sulfur based antibiotics (spectrogram, Kenacyn, Tetracycline, furan2 ask a friend if they have had luck with a specific brand). If your fish’s mouth is unaffected you may want to also give food medicated with oxytetracycline. Remember that some aquarium inhabitants like snails can die from the copper. Do not use your carbon during treatment. Follow antibiotic and copper sulfate packaging instructions closely. Copper sulfate is highly toxic to fish in very soft water below 50ppm CaC03.

Maintaining weekly water changes will help prevent bacteria from multiplying due to the fact that bacteria thrive on waste products. Disinfecting nets and containers before using them on different tanks will help prevent spreading bacteria from one place to another. If you have city water you can rinse your nets under the chlorinated water for a few minutes to help remove or kill some bacteria that may be present. Soaking in a 1:20 bleach solution followed by a thorough rinsing should kill anything that is on your equipment for sure.


Good photo of livebearer–’columnaris’