I had one way back when, it was pretty cool. mine was small and i only had it until it was about a foot long. it never ate any of my fish, at least not while they were alive ( there was an incedent where he ate an already dead fish that was killed by something else). again they wont harm corals, my hermits were never touched. crabs were eaten but i had a cleaner shrimp that was never harmed, it actually cleaned off his head, and it was added after the eel.