My red tailed shark has his fins clamped and is flashing quite a bit. His top fin is a bit roughed up but I assume that's from the flashing. There's about .5 ppm of ammonia in the tank right now. All of the other fish are fine and there's no sign of ich or velvet on any of them. Why is it only my rts doing this. Seems that I've had nothing but bad luck with keeping red tailed sharks. Please help.