Yellow coris wrasse

Geographic Origin and Biotope: Western and Eastern Pacific Ocean, including the coasts of Japan and Australia. Incessantly patrols coral reefs, sandy areas mixed with rubble and algae beds in search of small benthic invertebrates.

Taxonomy and Morphology: Yellow Coris Wrasse (Yellow Wrasse). Falsely known as "Coris", it belongs to the genus Halichoeres. Very hydrodynamic, slender and compressed, cigar-shaped body, specially evolved to cleave through the sand. Length 12 cm (4.7 inches).

Social Behavior: Very lively, peaceful and diurnal. Swims darting up and down the reef all day long. As soon as the lights go out (or if frightened), it dives headlong "like a dart" into the sand, burying itself completely to sleep safely.

Coloration and Sexual Dimorphism: Juveniles and females are a blazing solar yellow, with two evident false eyes (black ocelli) on the dorsal fin. As they grow and transform into terminal males, they lose the ocelli and develop thin dark green and pink vermiculations on the snout.

Aquarium Setup: Minimum 200-liter (55 gallons) reef. SAND REQUIREMENT: the bottom MUST be fine sand, at least 5-7 cm (2-3 inches) deep to allow nocturnal burial. Without sand it will stress to death breaking its snout on the glass or throw itself out of the tank. Lid absolutely necessary.

Diet and Feeding: Carnivore, tireless hunter of parasites. Easily accepts dry food (marine pellets, flakes), but must receive abundant frozen mysis and brine shrimp. Spends the day inspecting the rocks in search of plankton, eggs and parasites.

Water Quality: Extremely tolerant and robust (excellent for reef beginners). Temperature 24-27°C (75-81°F), specific gravity 1.023-1.025, pH 8.1-8.4. Actively contributes to the health of the aquarium by feeding on unwanted organisms that escape maintenance.

Compatibility and Tankmates: The "Medic Fish" of the Reef: it is formidable for eradicating plagues such as red planaria (flatworms), montipora-eating nudibranchs and pyramidellid snails of tridacnas. Safe with all corals, but may bother small shrimp or delicate decorative tube worms.

Aquarium Reproduction: Unknown in the home environment. Protogynous hermaphrodites (born female and change into males). In nature, mating takes place in the pelagic water column with the release of scattering eggs.

Risks and Diseases: Transport is very stressful (often travels buried in sand without eating). During the first week of introduction it may never come out of the sand for days. Stirring the sand to look for it means condemning it to death from a heart attack.