I noticed this morning this white, maybe cottony growth on one of my rasboras fins, and I'm not sure what it is. I was thinking it could be columnaris, but I can't tell.
He is in a 20 gallon long aquarium with 3 other rasboras, 5 corydoras, 1 male betta, 4 kuhli loaches, 2 bamboo shrimp, and...