They are sought after in the aquarium trade for their diet of nuisance bubble algae and other algae in general. They are voracious algae eaters and very docile.This crabs come in on alot of the live rock from floridaliverock. They cling to rockwork as they forage and they move very slowly.If you want one with you r order and to be sure let me know and I will add a free one to you r box . More than one can be kept in the same tank. They are also good scavengers.Crabs belong to the Class Crustacea and Order Decapoda, which is characterized by two pair of antennae, three body parts, and five pairs of legs.