We had a tank with some angel fish and tetras but found some angels that we wanted and got 2. One of those fish seemed normal for being put into a new tank for the first day or so but after a few days he didn't eat. He hasn't been eating for days now and is starting to thin out, he has clamped find and sits by himself in the corner, floating up and down slowly. The other fish we got seems to have no problems what so ever.