Inoticed my fish has holes on the side of its "gills" and i do not know if it is a disease. i do not see it on any of the other fish, and i keep the amonia levels how they should be., i have a filter, and i make sure i keep the water clean. i do not know what is wrong with it. the gill looks kind of puffy.

Symptoms of Sick Fish ... usually it's after a water change where the oxygen level's he's used to have changed or some other water metric. Gills that are puffy or swollen. Do your fishes gills look puffy or swollen? Is the gill tissue is bright red or even a grayish color? This is a good indication that something is wrong with your water.

osha website is the answer