When I first put my finger leather in the tank, my emerald nipped at it for a couple days. There was a rubber band securing it to the rock that I think he was more interested in. I haven't noticed anything since I removed it though.
I have two emeralds in my aquarium and until recently had not had any problems but 2 days ago I noticed one of mine pull a section of my green star polyp from a rock and eat it. i have had this crab for probably 2 years and until recently i had never had a problem with him.
hope this stops!!
I've seen my emerald crab "pick on" some of my corals, but they are never damaged. I think what is happening is the crab is picking off detritus that is so small we can't see it.