My Mbu is about 5" and seems to be fine but there are a couple things that have been worrying me. First, his habits are rather strange. He stays to one corner of the tank (75g) and will only swim at the front of the tank. He'll go to the halfway mark but then swim back to his corner. He either rests on the bottom near his corner or swims almost frantically at the glass. He also seems to be rubbing his mouth on the glass a little bit which leads me to my real concern. The skin around his mouth seems thinner and a bit whiter than the rest. At the corners of his mouth he has little holes in the skin, one on each side, that seem symmetrical and almost natural. I can't tell if the skin is receding but it definitely looks thinner than I've seen in Mbu pictures. He has a healthy appetite (thawed raw shrimp and earthworms mostly) and shows no other signs of distress. His breathing is heavy, but seems in pace with most puffers I've seen. I've been salting the water a bit as he had a little ich about a month back. Does this all sound normal? maybe I'm just paranoid but any help would be great.