If they are in the ten gallon in your signature, they are not going to do well bvery long at all, a 10 gallon is far, far to small for these fish. Have you tested water parameters? He could be sufferening from poisoning (ammonia or nitrites) or he could be suffering from a lack of oxygen or he could just be extremely unhappy in such a small tank, one should be kept in a tank of at least 40 gallons. They get to be about 15" when fully grown.
\Dan
