Here is a video of what 2 fang's puffers did to the tails of my larger cichlids. Needless to say, I isolated them after I noticed the damage and returned the little boogers back to the store. Didn't realize how aggressive they could be, but nevertheless, I was curious. Never again. I hope my fish can grow out their fins the way they were before, but I know it will take time.
http://www.youtube.com/watch?v=7G2ZeruitTI&feature=youtu.be