I recently had a valentini puffer mutilate a small clownfish, bit off easily 90% of all of its fins, and just noticed today that a lot of it grew back. It was hard to see because he is so small and the fins are very transparent. It doesn't help that he temporarily living in the sump. Yes the sump. It was the only place I could put him without the others killing him. I used no medication or special treatment. Just dropped him in there, prayed for the best, feed him, and slowly but surely he is making a full recovery!!! Not too bad for a fish that when I found him, the puffer was destroying him, he was just hovering across the bottom, and I was sure he was going to die that night, but couldn't give up on the poor guy!