I got a siamese flying fox yesterday. He looked healthy enough in the store, but then I couldn't get a very good look at him, so I might be mistaken. Anyway, I acclimated him to a cycled tank with 0 ammonia, 0 nitrite, and 10 nitrate. He had the appearance of swimming very hard but wasn't actually moving, just beating his pectoral fins and kind of gasping. He seemed to settle down, and then started doing it again. Today, minutes ago, when I went to feed the fish I saw him lying on his side on the sand, gasping and listless. Every minute or so he starts bolting around the tank, but he can't keep himself upright and just careens around upside down. Then he peters out and sinks again, upside down. It's not like any swim bladder issue I've ever seen. I'm afraid he doesn't have long to live, and I don't think I can do anything to save him. However, I really want to know what's wrong with him so I can treat my other fish accordingly and prevent it in the future. Please help!