You have be warned. No emerald crabs in LPS tank especially if you have chalices, scoly, or acans. They pick on them, play with them, turn them upside down, and poke them until they show skeletons and die.
I never had issues with them. Have seen several posts on it, so it does happen. But if there is not enough for them to eat i guess like anything. They will resort to that. I have noticed the males are more inclined to toss around a plug then the smaller clawed females. But females are not good at getting rid of bubble algae.