Yellowtail damselfish

Geographic Origin and Biotope: Western Pacific Ocean (Philippines, Indonesia, New Guinea). Lives in lagoons rich in branching corals at very shallow depths (1-15 meters).

Taxonomy and Morphology: Yellowtail Damselfish (Chrysiptera parasema). Stocky and very small marine damselfish (Pomacentridae) (max 7 cm / 2.7 inches). Do not confuse it with the similar Pomacentrus coelestis (which is less peaceful and has a yellow belly).

Social Behavior: Unlike other terrorist damselfish, C. parasema is considered the "least aggressive". However, it is strongly territorial. Always stays very close to its coral or rocky den.

Coloration and Sexual Dimorphism: Hypnotic livery: bright and phosphorescent indigo blue body, with the entire caudal fin (and peduncle) of a clear sun yellow. No visible sexual dimorphism.

Aquarium Setup: Acceptable in nano marine reefs (minimum 60-80 liters / 15-20 gallons). Requires densely arranged live rocks. If kept in a group (possible only in tanks >200L / 55 gallons) many corals (Acropora) are needed to divide the territories.

Diet and Feeding: Omnivore and easy to feed. Avidly consumes mysis, brine shrimp, fish eggs and commercial flakes or granules. Occasionally grazes film algae and zooplankton from the rocks.

Water Quality: Marine (salinity 1.024-1.026). Extremely hardy fish, famous for its tolerance to slight water imperfections (it is often used, although ethically discouraged, to start the cycling of marine tanks).

Compatibility and Tankmates: 100% Reef-Safe. Tolerant with most peaceful marine fish (Blennies, Gobies, Clownfish). Can become belligerent towards fish inserted *after* her that invade her rock.

Aquarium Reproduction: Possible but very rare. The male cleans a crevice and attracts the female by changing shades of color. The eggs adhere to the rock and are guarded. The pelagic larvae require rotifers at the very first stage.

Risks and Diseases: Very robust to marine fish diseases (Ich, Oodinium). The main risk is that if kept in small groups in 100 liter tanks, the hierarchy ends with the death of the weakest damselfish by submission.