I recently got some emerald crabs to help clean up my bubble algae. Despite after initially eating some algae, they've all one by one gone after just my cherry red Goniapora, despite some other easier target gonis and corals in the tank. Had anyone else seen this sort of specificity? I've managed to pull them all out at least but my poor goni is so gun shy now that if the fish swim near it, it pulls in 
