Hidden Hermit Crab

Geographical Origin and Habitat: Widely distributed in the tropical Indo-Pacific, from East Africa and the Red Sea to Hawaii, Australia, and the Tuamotu Islands. Inhabits shallow coral reefs, lagoons, and rocky tide pools.

Taxonomy: Member of the family Diogenidae. Features a soft abdomen protected by empty gastropod shells that it exchanges as it grows. Left claw is slightly larger than the right. Grows to 2.5-3 cm.

Social Behavior: Peaceful, active, and busy. Constantly searches rocks and sandy substrate for detritus. At night, they may aggregate in groups on high rock structures.

Coloration and Sexual Dimorphism: Body color is greyish-olive or brown. Recognized by the bright orange-brown tips on its walking legs (resembling socks) and blue-green eyes. No visible sexual dimorphism.

Tank Setup: Suitable for reef tanks or nano reefs of 8 gallons or larger. Provide live rock for climbing and forage. Empty gastropod shells of various sizes must be added to allow growth.

Diet and Feeding: Opportunistic herbivore and detritivore. Consumes green hair algae, film algae, and cyanobacteria. Accepts sinking pellets, spirulina tablets, and leftover frozen foods.

Water Quality: Stable reef parameters: SG 1.020-1.025, pH 8.1-8.4, temperature 22-28°C. Highly sensitive to copper treatments and elevated nitrates.

Compatibility and Tankmates: 100% reef-safe. Great Clean-Up Crew (CUC) member. Compatible with peaceful fish and corals. May occasionally target small live snails (like Cerithium) if empty shells are lacking.

Aquarium Breeding: Very difficult. Fertile eggs hatch into planktonic zoeal larvae that require specialized feeding and are usually removed by standard filtration.

Risks and Diseases: High stress and mortality if suitable replacement shells are unavailable. Highly sensitive to rapid salinity changes and copper treatments.