I just found this little fella on one of my corals. It looks like a very small crab. I thought a small emerald crab as I have 2 in my tank. He has been isolated for the time being
Any ideas please is he good or bad ?
Looks like it might be the Common Hairy Crab, Pilumnus vespertilio - not reef-safe, but would be a cool sump monster:
"In general, P. vespertilio consumes a wide range of foods, including crustose coralline algae and various other kinds of red/green/brown algae [2][22]. It is also known to prey on several intertidal animals, including brittle stars, marine gastropods (sea snails), bivalves (clams), bristle worms, and sea slugs [2][22]. In addition, they may also consume toxic zoanthids, which may make some members of this species mildly poisonous[4]."