i have a moroon clown in my 40 gallon tank and a few times he would randomly get beat up fins. It might have been my coral banded shrimp that gave him once slice, and then since he likes to swim in the current all day they got much more torn up. Im not sure how it started. It had happened two or three times since i got him. I jsut feed him formula one, prime reef, and the eyes of krill that fall off that i use to fed my snowflake. Sometimes ill give him a small piece of squid. But they always heal back. :happyfish