Due to the death of Colts, and how serious Columnaris is, I thought I would post this excerpt from "Friends of Fish". The actual post is way too long, but I recommend going there and reading it. Very thorough.
(Article link is after the picture.)
What is Columnaris?
Columnaris is a disease that goes by many names. Flexibacter, mouth rot, mouth fungus, gill fungus, body fungus, saddleback columnaris, and cotton wool disease: all of these common terms describe one tenacious bacteria, Flavobacterium columnare
, previously known as Flexibacter columnaris.
This gram-negative, motile, rod-shaped bacteria thrives in many of the same conditions that our tropical fish also enjoy, making it especially dangerous and virulent to stressed fish. Two primary strains exist, both with potentially devastating internal and external symptoms. One is slow-developing, with symptoms appearing over several days and more easily quelled by treatment. The other can kill within hours, and is known for creating massive losses due to its extreme virulence. Regardless of the strain or progression of the disease, columnaris is nothing to be taken lightly.
Betta with Columnaris