Emerald Crab (Mithraculus sculptus) Care Guide

A small, bright green crab valued for its appetite for bubble algae (Valonia), a common pest in reef tanks.

Overview

Mithraculus sculptus is a species in the family Mithracidae. A small, bright green crab valued for its appetite for bubble algae (Valonia), a common pest in reef tanks. Generally reef-safe but may become opportunistic in poorly fed tanks, occasionally picking at corals or small invertebrates. Best kept singly per tank.

Taxonomy

Family: Mithracidae
Genus: Mithraculus
Scientific name: Mithraculus sculptus
Other names: Emerald Mythrax Crab
Origin: Caribbean, Western Atlantic

Habitat

Mithraculus sculptus, the emerald crab, is found on reefs of the Caribbean and western Atlantic. It grazes algae, including bubble algae, and scavenges; generally reef-safe, though large or underfed individuals can occasionally harass small invertebrates.

Tank requirements

Minimum tank volume: 40 L
Temperature: 24-27 °C
pH: 8.1-8.4
Salinity: SG 1.024-1.026
KH: 8-12 dKH
Water flow: moderate
Adult size: 2-5 cm
Lifespan: 2-4 years
Difficulty: beginner

Diet

Classified as herbivore. Recommended feeding frequency: 1x daily. In captivity, offer a varied diet appropriate to the species — quality prepared foods supplemented with frozen or live items of suitable size.

Compatibility

Temperament: peaceful
Position in tank: bottom
Compatible tank mates: Clownfish, Blue Chromis, Firefish Goby, Snails
Avoid with: Other Emerald Crabs, Triggerfish

Reef compatibility

Generally classified as reef-safe with caution: may disturb other sessile invertebrates, sting neighbouring corals or prey on small ornamental shrimps, so placement and tankmates need consideration.