Black-Axil Chromis (Chromis atripectoralis) Care Guide
Chromis atripectoralis is a peaceful Indo-Pacific damselfish almost identical to Chromis viridis but distinguished by a black mark at the pectoral fin base.
Compiled by Aquairi from published sources · Published · Updated
Overview
Chromis atripectoralis, the black-axil chromis, is an Indo-Pacific damselfish of the family Pomacentridae. It is a sibling species of Chromis viridis, distinguished by a distinctly black pectoral fin axil where C. viridis is dusky with black dots. It also has 18-20 pectoral rays versus 17-19 in C. viridis.
Taxonomy
- Family: Pomacentridae
- Genus: Chromis
- Scientific name: Chromis atripectoralis
Habitat
The species ranges through the Indo-Pacific, across most islands of Oceania (except Hawaii, the Marquesas and the Pitcairn group) and into the Indian Ocean. It occupies clear lagoons, passages and seaward reef slopes at depths of 1-29 m, congregating in large groups above staghorn Acropora corals.
Tank requirements
- Minimum tank volume: 200 L
- Temperature: 24-26 °C (75-79 °F)
- pH: 8.1-8.4
- Specific gravity: 1.024-1.026
- Carbonate hardness (dKH): 8-12
- School size: 6 or more individuals
- Adult size: up to about 12 cm
- Lifespan: 8-15 years
Diet
Stomach analysis shows the wild diet is dominated by small crustaceans including copepods, amphipods and zoea. In the aquarium an omnivorous diet of small frozen and prepared marine foods fed two times daily is appropriate.
Compatibility
A peaceful mid-water schooling fish that suits community reef systems with clownfish, tangs, wrasses and gobies. Aggressive damselfish and predators such as lionfish should be avoided.
Reef compatibility
The black-axil chromis is reef-safe. It feeds in the water column above corals and does not harm corals or invertebrates, fitting well into reef aquariums with moderate flow.
Breeding
During the breeding season males pair and provide parental care, guarding and aerating demersal eggs adhered to the substrate. Captive breeding is considered difficult.
Black-Axil Chromis (Chromis atripectoralis) Breeding Guide
Overview
Chromis atripectoralis Welander & Schultz, 1951, the black-axil chromis, is an Indo-Pacific species ranging from the East African coast to French Polynesia and north to the Ryukyu Islands, reaching about 12 cm total length. It is nearly identical to C. viridis but bears a small black mark at the base of the pectoral fin. FishBase records it as oviparous with monogamous pairing during breeding, following the family's demersal-spawning, male-guarded pattern. IUCN assessed it as Least Concern in 2022.
Sexing
No reliable external sexing character is documented for C. atripectoralis in the consulted sources, and the species is broadly monomorphic. As in the closely related C. viridis, the nest-preparing, guarding individual is the male during reproduction.
Conditioning
A species-specific conditioning protocol is not documented. C. atripectoralis is planktivorous (trophic level about 3.1), feeding on copepods, amphipods and larvae and forming large aggregations above staghorn Acropora; a varied diet of small marine planktonic foods conditions a peaceful group. Maintain stable reef parameters within the recorded ranges (temperature about 24–26 °C, pH 8.1–8.4) and keep it as a school.
Breeding Setup
Provide open rock and rubble near branching coral, echoing the species' coral-thicket habitat, so a dominant male can establish and clean a nest patch. The family pattern has the male clear the area of algae and invertebrates. Keeping a group raises the chance of a pair forming; this is a relatively peaceful chromis.
Spawning Behavior & Trigger
Specific spawning triggers for C. atripectoralis are not documented. In Pomacentridae, ritualised courtship precedes spawning; the female lays a string of sticky eggs attached to the substrate and the male fertilises them externally. FishBase confirms the eggs are demersal and adhere to the substrate and that males guard and aerate them.
Egg & Fry Care
The male guards and aerates the clutch through incubation. At family level, eggs hatch over about two to seven days into transparent larvae roughly 2–4 mm long that enter a pelagic phase; late-stage larvae are strong swimmers documented at about 21.6–25.2 cm per second. This planktonic stage is the principal barrier to captive reproduction.