The Black Longspine Urchin is especially useful in reef aquariums because it will eat unsightly Green Hair Algae. It is also useful for controlling algae in aquariums containing aggressive fish. When they feel threatened by a fish they will actually point their spines at the fish to protect themselves.
They are venomous so be careful not to get poked. The sting is similar to a bee sting.
Longspine urchins are nocturnal although you will see them during the day. You may supplement their diet with dried seaweed (nori).