Bicolour Chromis

Bicolour Chromis

The Bicolour Chromis (Pycnochromis margaritifer, formerly Chromis margaritifer) is a small, crisply marked damselfish with a sharp two-tone pattern — a deep black front half meeting a clean white rear, divided as if painted. It is sometimes called the half-and-half chromis for exactly this reason. Active, hardy and inexpensive, it makes a smart, graphic addition to a reef community, especially when kept in a small group.

It is closely related to the more familiar green chromis but offers a bolder, more contrasting look in the aquarium.

Natural Habitat & Origin

Pycnochromis margaritifer is widespread through the tropical central Indo-Pacific, out to the oceanic islands of the central Pacific. It lives on coral reefs, typically hovering in loose aggregations above branching coral and rock, into which it dives for shelter when threatened.

In the aquarium it appreciates branching rockwork or coral for cover and open water above it in which to feed and shoal.

Care Requirements

Maintain stable marine conditions: salinity around 1.024–1.026, pH 8.1–8.4, and a temperature of about 24–26°C (75–79°F). Reaching only about 9 cm (3.5 inches) and best kept in a small group, it suits a tank of around 115 litres (30 US gallons) or more. It is hardy and adaptable, tolerating typical reef conditions well.

Diet & Feeding

The Bicolour Chromis is an omnivore, feeding on zooplankton and algae in the wild. It readily takes aquarium foods: offer frozen mysis and brine shrimp, quality marine flakes and small pellets, and foods with marine algae content. Feed small amounts a couple of times a day; it is an easy, eager feeder.

Behavior & Temperament

This is a mostly peaceful damselfish, more easygoing than many of its relatives, though as with all chromis a degree of squabbling can occur within a group as a pecking order forms. Keeping five or more helps spread out any aggression. It poses no real threat to other tankmates and spends its time feeding in open water and sheltering in the rocks.

Tank Mates

Good companions are other peaceful reef fish — clownfish, other chromis, gobies, smaller wrasses, cardinalfish and anthias. Avoid large aggressive species. It is fully reef-safe, leaving corals and invertebrates alone, and a small shoal makes a lively, attractive display in a community reef.

Breeding

Like other damselfish, P. margaritifer lays demersal eggs guarded by the male, but rearing the pelagic larvae is rarely accomplished in the home aquarium. Trade specimens are wild-collected.

Common Health Issues

The Bicolour Chromis is hardy but, like all marine fish, can be affected by marine ich (Cryptocaryon irritans) and marine velvet (Amyloodinium ocellatum) under stress. Quarantine new arrivals, keep water quality stable, and keep it in a group to reduce stress and aggression. Given those basics it is a dependable, beginner-friendly and visually striking addition to a peaceful reef.