Mithrax sculptus

(Lamarck, 1818)

Emerald Crab

Range: Tropical Western Atlantic Ocean: Florida Keys, and the Caribbean.

Size: 3 - 4 inches (7.5 - 10 cm)

Natural Environment: This large bodied species with sizeable forearms and claws is usually found living on algae covered rocky coastlines, backwater areas where rock surfaces and rubble are algae covered and seagrass beds.

General Husbandry: These heavily armored crabs have a shinny green carapace and claws, with hairy, dark green walking legs. Their claws have blunt tips, which are used for feeding on different forms of algae, including bubble algae (Valonia).

Though thought to be reef safe, yet larger specimens may turn into a predatory creature and eat small fish, and possibly other small animals in the aquarium. In fact, anything with a claw that does not have its fill of its normal foods found in the wild, will turn towards other sources of food, tasty or not! Therefore, this is not a 'totally' reef safe animal, and even if kept in a fish-only aquarium, thought should be given to what size and type fishes are maintained in that system.

As for feeding, they are not fussy eaters, as small members will scavenge various forms of algae, but more mature ones may turn to other foodstuffs if they do not have an adequate supply of algae. Therefore, in systems somewhat devoid of algae, plant rocks, e.g., those covered with different forms of algae (micro or macro) and/or Nori (Sheets of dry algae) may be a way of satisfying their nutritional needs, thereby preventing them from turning to other forms of food for nourishment.

Taxonomy:

Kingdom: Animalia

Phylum: Arthropoda

Class: Malacostraca

Subclass: Eumalacostraca

Order: Decapoda

Superfamily: Majoidea

Family: Mithracidae

Genus: Mithrax

FYI: Actually, an Omnivore, even though sometimes sold as an Herbivore.

Not fussy about water quality.

Experience Level: Beginner

Diet: Omnivore/Mainly algae

Temperament: Semi-aggressive

Aquarium Environment: Reef or fish-only aquarium

Coral Safe: Yes

Fish Safe: With caution

Invertebrate Safe: Yes

Temperature Range: 72 - 82°F (22 - 27°C)