Common Name: Also known a Mouth Fungus, Columnaris is actually a bacterial infection, not a true fungus.

Pathogen/Cause: Flexibacter columnaris is a gram positive bacteria.

Physical Signs: Typically you'll see white, or semi-transparent strings of what look like fuzz in the mouth/gill area. Sometimes there will be white, clear, or reddish/pink sores on the body. Sometimes deep ulcers and inflammed patches develop on the body and fins of the fish.

Behavioral Signs: Most times fish will be lethargic and won't eat.  Sometime they will also be breathing heavily and fast.

Potential Treatment:  In my experience, I've only been able to cure a columnaris infection with salt baths and increased temperature and salinity in the hospital tank.  Of course, you can try any aquarium anti-biotic that is for gram positive bacteria, but I would also increase salinity and do salt baths (if fish isn't too far gone).


How to do a Salt Bath for your sick fish.