I noticed today that one of my red fin sharks has what looks to be a cloudy white almost brownish "crud" (for lack of a better word) on/in his gill on one side. He doesn't appear to be acting differently, and he's eating fine. To be honest with me it looks like a piece of pellet food is stuck in his gill although they don't eat pellets. I'm looking for any information as to what this may be as soon as possible. I'm concerned for my other fish. Thanks alot everyone!