I actually had a fry with a tail just like that. I think what happened is the poor thing got caught up in some type of tank cleaning equipment or got hurt somehow before he got to PetCo. I've had Mars for about 4 months now & it's mostly fixed itself, although I doubt it will every go away completely. I would continue to keep an eye on it, but as long as their quality of life is good, I wouldn't worry about. It'll just be something that makes our fish more unique! :)
EDIT: I absolutely agree with everyone else, continue to keep her away from everyone until you're sure. Better safe than sorry.
Last edited by JessSH; 11-28-2012 at 02:33 AM.