Colin's Angelfish

Geographic Origin and Biotope: Western Indo-Pacific, including Cocos-Keeling Islands, Indonesia, Philippines, Papua New Guinea, Palau, Guam, and Fiji. Inhabits steep drop-offs and outer reef slopes at depths of 20 to over 110 meters, living in deep caves and crevices.

Taxonomy and Morphology: Member of the family Pomacanthidae. A small pygmy angelfish with a laterally compressed oval body, reaching a maximum length of 9 cm. Features the characteristic preopercular spine.

Social Behavior: Highly cryptic and diurnal. Lives in small harems consisting of one dominant male and 2–6 females within coral caves. Often swims upside down along cave ceilings.

Coloration and Sexual Dimorphism: Body and head are a vivid lemon-yellow, contrasted by a prominent dark purplish-blue saddle running along the back and dorsal fin. A thin purple ring outlines the eye. No obvious sexual dimorphism except size.

Aquarium Setup: Requires an aquarium of at least 150 liters with extensive live rock arranged to create dark caves and overhangs. Prefers subdued lighting to mimic its deep-water habitat. A tight-fitting lid is recommended.

Diet and Feeding: Omnivore. Primarily feeds on sponges, tunicates, and algae in the wild. In aquariums, it must be offered sponge-based angelfish preparations, mysis, brine shrimp, and spirulina several times daily.

Water Quality: Demands cool, clean water and stable parameters. Temperature 21–25°C (70–77°F), 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: Best kept with peaceful, non-aggressive tankmates. Avoid active, boisterous feeders that may scare it. Reef-safe with caution: may nip at LPS corals and clam mantles if underfed.

Aquarium Reproduction: Extremely difficult and undocumented in home aquariums. Professional facilities have recently achieved success in raising captive-bred specimens.

Risks and Diseases: High risk of starvation if it refuses food due to stress. Susceptible to decompression issues if wild-caught, and highly prone to marine ich (Cryptocaryon) if water conditions fluctuate.