Emerald Crab

Emerald Crab – Mithraculus sculptus

The Emerald Crab is a vibrant green scavenger celebrated for its ability to consume leftover meaty foods and a wide range of nuisance algae, notably problematic bubble algae. Its flat, shiny emerald shell and fuzzy legs make it easy to identify as it explores your reefscape. Nocturnal by nature, it typically hides in rockwork during the day but often becomes more visible once acclimated. When well fed, it is a peaceful and effective member of a reef cleanup crew.

Emerald Crabs thrive in mature reef aquariums with abundant live rock, caves, and rubble zones that provide hiding spaces and natural grazing surfaces. Introduce them only after the tank has stabilized and developed sufficient algae growth—usually a few months after cycling. They require stable parameters and, like all invertebrates, must be protected from copper-based treatments.

Although they graze naturally, Emerald Crabs benefit from supplemental feeding to prevent opportunistic behavior. Offer dried seaweed, pellets, or finely chopped meaty foods from trusted brands such as San Francisco Bay, Hikari, PE Mysis, TDO, and New Life Spectrum.

Sizing Chart:
Approximate Purchase Size: 1/2" to 1-1/2"