Mithraculus sculptus

Acclimation: like other invertebrates, it copes badly with sudden water changes. Drip-acclimate it (one to two drops per second) until the salinity in the bucket matches the tank, then discard the shipping water.

Aquascape: it needs a well-established tank with plenty of rock and hiding places. Nocturnal, it hides by day at first; once settled it also forages in daylight. Its legs grip the rockwork firmly, which makes it hard to catch if it has to come out.

Tankmates: well fed, most individuals get along with their neighbours. Reports nevertheless describe zoanthids and soft corals torn apart and a clownfish with bitten fins, mostly at night. Watch it and remove it if it causes damage; a refugium or sump can host it without risk to the display.

Sensitivities: it tolerates neither copper treatments nor unstable parameters. Water: 22 to 25.5 °C, specific gravity 1.020 to 1.025, pH 8.1 to 8.4, alkalinity 8 to 12 dKH.

In the wild it is mainly a scavenger that also eats algae, in particular the organisms encrusting seagrass blades.

In the aquarium it eats leftover meaty food and many nuisance algae, including the bubble algae (Valonia) few animals touch; not every individual does so, and never enough to clear a heavy outbreak on its own. Food must be available at all times: add dried seaweed, chopped meaty food (shrimp, mysis) and a quality pellet. An underfed crab may turn to corals, invertebrates or small fish.