Blackaxil Chromis (Chromis atripectoralis)

Blackaxil Chromis Chromis atripectoralis
Name	Blackaxil Chromis
Name Lat.	Chromis atripectoralis
Family	Damselfishes
Family lat.	Pomacentridae
Order	Ovalentarias
Order lat.	Ovalentaria inc. sed.
Origin	Indo-West Pacific
Habitat	Lagoons, seaward reefs
Diet	Omnivore
pH	8.1-8.4
Hardness	8-10 °KH
Behavior	Peaceful
Keeping	Group
Reef Compatible	Yes
Care Level	Easy
Life Span	5-8 years
Protection	No
Metric Units
Size	11 cm
Temperature	23-28 °C
Salinity	33-36 ‰
Aquarium	~ 300 l
US Units
Size	4"
Temperature	73-82 °F
Salinity	1.020-1.025 sg
Aquarium	~ 80 gal

Distribution and habitat

The range of Chromis atripectoralis is the Indian and Pacific Oceans, from the Seychelles through Australia and Indonesia to southern Japan and most islands of Oceania. They live in large groups on coral-covered (acropores) outer reefs and in lagoons down to 30 m depth.

Maintenance

They need a well-structured aquarium with a reef structure that allows for territoriality and at the same time offers hiding, resting and covering possibilities, with living stones that act like a biological filter and sufficient swimming space. Only lime-rich, heavy metal-free substrates may be used as substrate

Filters, skimmers and heaters are necessary to ensure water quality, as well as pumps to simulate tides, swells and bottom currents. Lighting must match the species-appropriate day-night rhythm of the animals

Salinity: 33-36 ‰	pH value: 8.1-8.4
Carbonate hardness: 8-10 °KH	Nitrate content: 2-8 mg/l
phosphate content: 0.01-0.1 mg/l	nitrite content: 0.0-0.05 mg/l

For salinity, an average value should be aimed for, which may only vary slightly by +/- 0.5 ‰. Ammonia and ammonium must not be measurable. Special attention must be paid to constantly good water quality.

Diet

They feed mainly on zooplankton, but also need plant food. The feed change usually succeeds without problems. The food supply should consist of a commercially available vitamin-enriched frozen special food mixture for plankton eaters or a combination of algae (e.g. spirulina, kelp) with live and frozen food, such as small mysis, krill, bosmids, cyclops and artemia. In addition, high-quality dry food in flake or granular form with a high vegetable content can be offered, which is usually well accepted. It is recommended to feed small portions several times a day (3-5 times).

Regular and varied feeding promotes health and increases resistance.

Behaviour and compatibility

They should be maintained only in a group of at least 3-5 animals. To avoid ranking fights, they should be introduced into the aquarium at the same time. Dominant males behave territorially at spawning time and consistently defend their territory. They can be well socialized with other peaceful fish.

Sex dimorphism

There are no known external distinguishing characteristics.

Reproduction and breeding

There are isolated reports of successful breeding in the aquarium.

Important

Juveniles lack the black spot at the pectoral fin base and can therefore be easily confused with Chromis viridis. Due to different areas of origin their coloration varies. It is recommended to keep these reef dwellers together with corals, especially acropores, and not to keep them in a fish-only aquarium.

If different species are kept together, care should be taken to match the fish in terms of water quality and temperature requirements and social behavior, and to ensure that the setup meets the needs of all species kept together. Newly introduced fish must be acclimated slowly to the water in the aquarium

Further literature can be found in your pet store.

References

Text: Werner Winter; Image: Franz Lowak

Source: KUITER, DEBELIUS (2007): Atlas der Meeresfische: Die Fische an den Küsten der Weltmeere, Kosmos Verlag; BAENSCH & PATZNER (1998): Meerwasser Atlas Bd. 7, Mergus Verlag; ENGELMANN (2005): Zootierhaltung - Tiere in menschlicher Obhut: Fische, Verlag Harri Deutsch

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