I would just place him in a tank by himself, if for no other reason that he won't get eaten or beaten up.

My neighbour had a tetra that swam like that for years. It was some type of genetic problem. It was never contagious, but if your fish never came that way, then its probably been severly injured or it has an undiagnosed disease. So quarantine it. That's what I would do. You may also ask your petstore for advice. They should know what to do.

Dasheen

Since posting this message the other fish have eaten his tailfin completely off. He currently spends most of his time hiding behind the heater. If I move him to another tank, will the tailfins grow back?

Tailfins and other fins definitely grow back...if it's just that he's being nipped. If it's fin rot or something like that, then you'll need to medicate the tank.

Good luck!

-PF

I would medicate if I wee you, under high stress it may have been bacteria that ate off his tail fin, fin rot is quite common in aquaria. But if he is seperated and infection doesn't kill him his fins should grow back in a jiff, so long as the base is there.

It appears that his fin is starting to grow back. He's been hiding behind the heater where the other fish can't get to his fin. I'm hoping for a full recovery.

I would still move him. I have ciclids too and every time I see one get beat up or something just as unkind they eventully get killed by the other fish. He's weak right now and one of the other fish will sneak up on him. Move him and give him a chance to recover.