When I had one he was around 3 to 4 inches and he ate what ever he could catch.Shrimp,hermits,snails,whatever he decided to eat that day.I can't say anything about coral cause he was in a fowlr.BUT with this hobby, you never know,each animal has its own personality.
A buddy of mine had/has one. He assumes it's still in there because his inverts keep vanishing. He has seen it twice in 6 months, in a 150 reef. He wants to get rid of it but he can't find it. Cool looking but very secretive. Not invert safe.
Yeah, I think those purple reef lobsters are just better off being left in the ocean. I bought live rock one time and there was a purple lobster in one of the holes that refused to come out. The guy at the LFS tried everything and eventually he just convinced me to buy the lobster and the rock telling me that he would cruise around the tank and take food from tongs. Lobster never came out and I could never find him. Total waste.
I have one. Hes in a 55 reef with a cleaner, fire & some pep shrimps. He has never gone after any of them. Also have a clam and some corals which he doesnt seem to touch. He is 4 inchs and stays hidden all day.
I try to spot feed him some pellets every once in awhile and I bet he catchs some mysis when I feed them.
I got one that was about 2-3" that came as a hitchhiker from AquaHuts LR. Within 5 minutes of getting in the tank, it ate my mandarin.
I've heard people say that they eat Sailfin tangs, shrimp, snails, etc.