One of my goldfish is the weirdest fish I've ever seen. This fish gulps air on a regular basis, seemingly to try and kill himself. But then he gets rid of it and is fine, for a while. Lately, he's taken to spending nights floating upside down, simulating a dead fish. But by afternoon, he's swimming and completely in control of his air bladder. If fish had looney-bins, I'd have him committed.