Emerald Crab

Emerald Crab – Saltwater Cleanup Crew

Mithraculus sculptus

Other Common Names: Emerald Mithrax Crab, Green Mithrax Crab, Emerald Mythrax Crab

Origin: USA / Western Atlantic
Care Level: Easy
Reef Safe: Generally, with caution
Temperament: Semi-Aggressive / Opportunistic
Maximum Size: Approximately 2–2.5 inches

The Emerald Crab is one of the most popular and useful members of a saltwater aquarium cleanup crew. Recognized by its distinctive green body and hairy legs, this hardy crab spends much of its time exploring live rock, grazing on nuisance algae, and scavenging leftover food.

Emerald Crabs are especially popular for their ability to consume bubble algae (Valonia), a stubborn nuisance algae that many other cleanup-crew animals ignore. While they can be effective at controlling bubble algae, individual feeding preferences vary and complete removal is not guaranteed.

Generally suitable for established reef aquariums, Emerald Crabs are opportunistic omnivores. If food becomes scarce, they may pick at corals, other invertebrates, or vulnerable fish. Providing supplemental food helps reduce unwanted behavior.

Aquarium Requirements:

• Established saltwater aquarium with live rock

• Plenty of crevices and hiding places

• Stable salinity and water parameters

• Peaceful tankmates that will not prey on crabs

Diet: Bubble algae, film algae, some nuisance hair algae, detritus, and leftover foods. Supplement with dried seaweed, quality marine pellets, and occasional meaty foods when natural algae is limited.

Important: Emerald Crabs are sensitive to copper-based medications and rapid changes in salinity. Acclimate carefully before introducing them to your aquarium.

An excellent addition to many saltwater cleanup crews, particularly aquariums struggling with bubble algae.