comet leaning over while swimming

Hm... leaning over sideways or standing on his head, or what? It could just be a fluke, it could be that he's having buoyancy problems. Could also be a tumor. Is his appetite normal? Any other strange symptoms?

thanks flarringshutter, I was really hoping you would see this. He started about 3 or 4 days ago. His appetite does seem to be normal, doesnt seem like he has any bouncy issues, no standing on his head. when he sits still, he is not leaning.
only other issue is he as a little rip at the tip of his tail fin, but he might have just snagged it on something. he loves to try and fit in places.

Didn't mean to leave you hanging here, the thread just got pushed under by a few new ones.
Anyway, from what you described I think it's probably nothing to worry about. As long as he's eating and his behavior is normal, I wouldn't worry too much. Keep an eye on him and if he starts leaning over more, or has any swimming problems, then it might be something serious.
I'd probably feed him a few cooked, shelled peas for a few days to clear out any gas bubbles he might have. It can't hurt and it might solve the issue.