So, I've been battling very stubborn fin rot with Ptolemy (he's a tail biter). Some may be aware of this. When I brought him home, at first we thought it was a blown out caudal fin, but then it became obvious that it was rot. Salt wasn't doing a thing, nor was Multi Cure though it did stop the spread, so now he's been on Tri Sulfa and aquarium salt for 6 days with positive results (I checked and you can safely mix the two).
But now I came home to find that he has a new problem. It can't be anything that Tri Sulfa takes care of (which means it's not white spot or mouth and body fungus or fin and tail rot), so what is it?
It's on the side of his body, in the middle, and it's looks as if he has something like flat dry glue stuck to three of his scales, or as if he scraped himself there or something. (Photo provided--the best I could take.)
Water parameters are all good. Temperature likewise.
Please help. He's finally got nice new fin regrowth, and now this happens.