The patches aren't fuzzy. I wouldn't even call them patches. More like scale discoloration. I put the filter in a few weeks ago but I believe it has been going on before the filter was placed in the tank and now I just noticed it since it's gotten larger. It's mainly on his sides and even light highlights of white in his tail. But the top of his gills have some dark white on them. There is no redness in his gills as far as I can tell because it is quite difficult to see since his colors are so dark. And my camera when I try to take a photo of him just makes him a black blob. Ugh... It's so strange though. He made a bubble nest earlier this week too. He's been eating fine. I don't know what to do.
Correct me if I am wrong, but as far as I know - ammonia burns are red.
I think the redness on his gill cover thingy and that scar like thing are caused by ammonia. The ammonia in his cup registered at an 8.0
This guy too:
Are these grey patches fuzzy? How long as your filter been running?