Squarespot Anthias

Geographical Origin and Habitat: Found in the Indo-West Pacific, from Indonesia and the Philippines to Samoa, north to southern Japan (Ryukyu Islands), and south to the Great Barrier Reef. Inhabits outer reef slopes and drop-offs at depths of 10 to 180 meters.

Taxonomy and Morphology: Member of the family Serranidae, subfamily Anthiadinae. It is one of the larger anthias species, reaching up to 20 cm in total length. Features a compressed, robust body with a deeply forked caudal fin.

Social Behavior: Lives in structured harems containing one dominant male and a group of females. Males defend their territory and harem from competing males. They swim in open water above the reef slopes.

Coloration and Sexual Dimorphism: Sexual dimorphism is highly pronounced. Males are bright pink-magenta with a distinctive purple-lilac square spot on their sides and blue-trimmed fins. Females are overall bright orange-yellow with violet lines running from the eye to the pectoral fins.

Aquarium Setup: Requires a spacious aquarium of at least 500 liters for a small harem. High water movement and excellent filtration are essential to handle organic wastes. Provide caves, overhangs, and shaded spots within the rockwork.

Diet and Feeding: Strictly zooplanktivorous. In captivity, must be fed 3 to 4 times daily with high-quality frozen foods like mysis, brine shrimp, calanus, and lobster eggs. They may be hesitant to accept dry food initially.

Water Quality: Demands pristine, highly oxygenated water. Temperature 22-27°C, pH 8.1-8.4, salinity SG 1.020-1.026. GH 15-25. A heavy-duty protein skimmer is vital to manage the high bioload from frequent feedings.

Compatibility and Cohabitation: 100% reef safe. Peaceful towards other non-conspecific reef fish. Avoid housing with overly aggressive species like dominant large surgeonfishes, which may intimidate them during feeding.

Aquarium Breeding: Extremely rare in captivity. They are protogynous hermaphrodites: if the male dies or is removed, the dominant female will transition into a male within a few weeks.

Risks and Diseases: The main threat is starvation due to inadequate feeding frequency. High stress during acclimation can make them susceptible to marine ich. A tight-fitting lid is mandatory as they are notorious jumpers.