Masked Angelfish

Geographic Origin and Biotope: Endemic to the Northwestern Hawaiian Islands and Midway Atoll. Inhabits deep seaward reefs and rocky slopes at depths from 20 to 174 meters in cool, current-swept waters.

Taxonomy and Morphology: Member of the family Pomacanthidae. Grows to a maximum length of 21 cm. Features a slender, compressed body with a swallowtail caudal fin characteristic of Genicanthus.

Social Behavior: Peaceful and active water-column swimmer. Sequential protogynous hermaphrodite: all start as females, and the dominant female transitions into a male. Lives in small harems.

Coloration and Sexual Dimorphism: Strongly sexually dimorphic. Females are pure pearly-white with a black mask around the eyes and a black-edged tail. Males develop bright yellow-orange borders on their fins and face.

Aquarium Setup: Requires a very large aquarium of at least 800 liters with vast open swimming space and live rock. A chiller is mandatory to keep the water temperature between 19–23°C (66–73°F). A secure lid is required.

Diet and Feeding: Omnivore/Planktivore. Feeds naturally on zooplankton and suspended algae. In captivity, feed 3–4 times daily with copepods, mysis, brine shrimp, calanus, and high-quality prepared foods.

Water Quality: Demands cool, clean water and stable parameters. Temperature 19–23°C, pH 8.1–8.4, salinity SG 1.020–1.025, GH 15–25, and KH 8–12. Sensitive to high nitrates.

Compatibility and Tankmates: Peaceful toward other tankmates. Completely reef-safe; it does not harm corals or sessile invertebrates.

Aquarium Reproduction: Extremely difficult. Only a few commercial breeders have successfully reared this species in captivity.

Risks and Diseases: Temperature stress is the primary threat. Prone to skin parasites (Cryptocaryon) if housed in warm water or unstable systems.