Black spiny urchin
I always read suggestions from others that Urchins are good algae eaters. Well, this urchin - Arbacia punctulata - sure seems to love coralline, the purplish algae I actually want! Oh well, its not doing too much damage over all, with 120lbs of LR in the tank. It travels over the rockwork and the glass, and hasn't been problem at all. It does knock over smaller frags like a bulldozer sometimes. Reef-safe.