Blue-eyed Coral Crab

Geographical Origin and Habitat: Widely distributed throughout the tropical Indo-Pacific, from East Africa and the Red Sea to Hawaii and Polynesia. Found strictly within live branching corals of the family Pocilloporidae.

Taxonomy: Member of the family Trapeziidae. Features a smooth, shiny trapezoidal carapace measuring about 2-3 cm in width. Legs are strong, with curved dactyli adapted for gripping coral branches. Grows to 2.5 cm.

Social Behavior: Highly protective mutualistic symbiont. Defends host corals from predators (like crown-of-thorns starfish) and parasites, while cleaning coral tissue. Commonly found in male-female pairs.

Coloration and Sexual Dimorphism: Body color is solid reddish-orange, pink, or rusty-orange. Distinguished by its striking, bright blue or light blue eyes. No visible sexual dimorphism.

Tank Setup: Must be housed in a mature reef aquarium of 15 gallons or larger with live, healthy branching corals (Pocillopora, Stylophora, or Seriatopora). Does not require empty shells.

Diet and Feeding: Feeds on coral mucus and organic detritus trapped between the coral branches. In aquariums, it also catches suspended food like mysis or brine shrimp from the water column.

Water Quality: Reef parameters. Salinity SG 1.021-1.025, pH 8.1-8.4, temperature 22-28°C. Highly sensitive to copper treatments, elevated nitrates, and sudden salinity drops.

Compatibility and Tankmates: 100% reef-safe. Mutualistic protector of its host coral. Compatible with peaceful reef fish. Avoid predatory tankmates (e.g. hawkfish, wrasses, or groupers).

Aquarium Breeding: Microscopic larval stages are pelagic and complex, and do not survive standard home aquarium filtration systems.

Risks and Diseases: Direct dependence on the host coral; if the coral host dies, the crab will experience high stress and likely perish. Requires stable calcium and iodine for molting.