okay, on my wolf fish (mala, so common wolf) on the left gill it almost looks like a small portion of his "skin peeled back and eventually fell off(last i knew the other day it was hanging and now it fell off)it also looks like it took off a layer off fat/muslce w.e is directly under the outter skin for the gill. i didn't think it'd be from him scraping anything since he has been in the same tank setup for almost a year now.