Blackeye thicklip

Geographical Origin and Habitat: Hemigymnus melapterus is widely distributed across the tropical Indo-Pacific, ranging from the coast of East Africa and the Red Sea to Micronesia, Polynesia, and the Great Barrier Reef of Australia. It inhabits coastal coral reefs, protected lagoons, and sandy areas adjacent to reef structures at depths from 1 to 30 meters. Juveniles are typically found in shallower habitats rich in algae and soft corals for camouflage.

Taxonomy and Morphology: This species belongs to the family Labridae. Described by Bloch in 1791, it is characterized by its exceptionally thick, fleshy lips that fold back, a feature that defines the genus. It has a robust, laterally compressed body and a large head. In the wild, it can grow to a massive size of 60 to 90 centimeters, though it usually remains smaller in aquarium environments.

Social Behavior: Juveniles are peaceful and tend to inhabit soft coral areas solitarily or in small groups. As they mature, they become solitary, highly active diurnal fish that constantly search the sandy substrate for prey, blowing water into the sand or overturning stones with their mouth to find benthic invertebrates. At night, they bury themselves in the sand to sleep.

Coloration and Sexual Dimorphism: Features a very sharp two-toned coloration: the anterior half of the body (head to anterior dorsal fin) is light greyish-green or white, while the posterior half is dark green or black. Juveniles show a vertical white band separating the two zones. There is no major sexual dimorphism, but dominant males may show brighter colors and blue facial markings during spawning.

Aquarium Setup: Due to its large adult size and active swimming behavior, it requires a giant marine aquarium of at least 800-1000 liters. It is absolutely mandatory to provide a deep bed of fine, non-sharp sand (at least 8-10 cm deep) on the tank bottom, as this fish needs to bury itself to sleep or when startled. Rockwork must be stable and placed directly on the bottom glass.

Diet and Feeding: A benthic carnivore with a large appetite. Its diet should consist of a variety of meaty frozen foods such as mysis shrimp, krill, whole shrimp, chopped clams, mussels, and squid. In the reef aquarium, it can help control populations of pyramidellid snails and bristleworms, but it will also consume any ornamental shrimp, crabs, or small mollusks.

Water Quality: Requires heavy filtration and a powerful protein skimmer to handle the large organic waste output of such a large fish. Water temperature should be kept between 24°C and 28°C, pH between 8.1 and 8.4, and specific gravity between 1.022 and 1.025. Nitrates and phosphates should be monitored closely and kept low through regular water changes.

Compatibility and Cohabitation: Because of its large size and active nature, it should not be housed with very small or slow-swimming fish, which may be intimidated or eaten. It is compatible with tangs, triggerfish, groupers, and other large wrasses. It is not reef-safe for tanks with benthic invertebrates, as it will eat ornamental shrimp, crabs, urchins, and snails.

Aquarium Breeding: Breeding in home aquaria is considered impossible due to the massive water volume required for courtship rituals and its complex pelagic larval phase. In nature, wrasses spawn at dusk in open water, releasing gametes into ocean currents that disperse the floating eggs until they hatch and develop.

Risks and Diseases: The primary risk in captivity is the lack of a suitable sand substrate, which leads to extreme stress, mouth damage, and death when the fish tries to bury itself. It is susceptible to marine ich (Cryptocaryon irritans) if stressed. Quarantine tanks must be equipped with a bowl of clean sand so the fish can sleep safely.