The Red Mithrax Crab , is a very popular aquarium species. These crabs have a distinct pre-historic look with their bumpy shells and hairy legs. They are completely off red in color and have flattened tips to their claws designed specifically to pull at algae. 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. They cling to rockwork as they forage and they move very slowly. 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. The head of a Crab is connected to the thorax and covered by a shell called carapace. They have a smaller abdomen and tail compared to Shrimp and they keep this tucked beneath the carapace. The first pair of their legs are usually developed claws which they use to gather food, use as protection, and to move objects. In order for Crabs to grow they need to shed their exoskeleton, a process called "molting", which allows them to remove their restricting shell and begin a new one. Often times in the home aquarium Crabs will leave this translucent shell in full view so it can serve as a distraction while the Crab finds a hiding place and allows its new shell to harden.Photo by Saltwaterfish.com member, Zexx: Natalie Cervantes.