I have a red tail shark in my tank, she still fairly new like most of my fish. I'm guessing that the red tail is female, my father looked up on signs, and stated it was a girl... But the yesterday she was swimming at the top of the tank upside down... That in its self isn't to weird I guess, but her belly was really big, and she's the only shark in the tank. She seems fine now but it was really odd. But I'd like to know what might have been wrong with her, should I be worried?