Eurysternus Hermit Crab

Geographical Origin and Habitat: Widely distributed in the tropical Indo-Pacific, from East Africa to the Philippines, Australia, and central Pacific islands. Inhabits coral reefs, rocky intertidal flats, and sandy tide pools.

Taxonomy: Member of the family Diogenidae. Features an elongated body and a soft abdomen protected by empty gastropod shells that it exchanges as it grows. Equal-sized claws. Grows to about 4 cm.

Social Behavior: Peaceful and active scavenger. Spends its time climbing rocks and substrate searching for food. May dispute empty shells with other hermit crabs if they are scarce.

Coloration and Sexual Dimorphism: Walking legs show a striking pattern of alternating longitudinal yellow, cream, and dark brown or black stripes. No obvious external sexual dimorphism.

Tank Setup: Suitable for marine tanks of 10 gallons or larger. Live rock is essential for climbing and grazing. It is mandatory to provide empty gastropod shells of various sizes for growth.

Diet and Feeding: Opportunistic detritivore and herbivore. Great for controlling hair algae and cyanobacteria. Accepts sinking pellets, leftover frozen foods, and dried seaweed (nori).

Water Quality: Standard marine 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. Perfect member of the clean-up crew (CUC). Compatible with peaceful fish and corals. May occasionally attack snails (like Turbo or Astrea) if it needs a new shell.

Aquarium Breeding: Very difficult in home systems. Spawning releases marine planktonic larvae (zoea) which require specific food and are usually removed by filtration.

Risks and Diseases: Lack of suitable shells causes high stress, mortality, or aggressive behavior towards live snails. Highly sensitive to rapid salinity changes.