Emerald Mithrax Crab

There are many different types of crabs for the marine reef aquarium. One of the most common crabs in the saltwater aquarium trade are the Emerald Mithrax Crabs.  These Crabs are typically obtained for controlling nuisance algae such as valonia otherwise known as bubble algae.

Emerald Crabs are native to the Caribbean and there formal name is Mithraculus sculptus.  They thrive in an environment with temperatures in the 75-78F range and a salinity factor of the average reef aquarium from 1.023-1.026.  They can get as big as 2.5 inches and are omnivorous.  They scavenge the reefs live rock for algae as well as meaty foods such as decaying fish.

Emerald crabs can show aggressive behavior but normally will only show it when acting in defense.  They often wave their claws around when fish or people come into their area or come close to the tank. Emerald Crabs may resort to feeding on corals or other invertebrates if not supplied with enough food.  If not enough food can be scavenged in your reef aquarium then it is suggest to supplement your emerald crabs with Nori, dried seaweed or a natural meaty food that would be available in their diet such as silversides.

The Following Video is one of my Emerald Mithrax Crabs hanging out picking algae of the side of the Aquarium Glass.