Black Axil Chromis

The Black Axil Chromis is a beautiful and hardy schooling fish often confused with the closely related Blue Green Chromis (Chromis viridis). Both species share a similar iridescent green body coloration, but the Black Axil Chromis is distinguished by a prominent black spot at the base of its pectoral fin, which is the defining characteristic that gives it its common name. This subtle difference is the key to telling the two species apart, along with the slightly more robust body shape of C. atripectoralis.

In the wild, Black Axil Chromis are widespread throughout the Indo-Pacific, from the Great Barrier Reef to Micronesia. They form large aggregations above branching corals on outer reef slopes and lagoons, feeding on zooplankton carried by currents. Their natural schooling behavior is one of the quintessential sights of a healthy coral reef, with hundreds of shimmering green fish moving in coordinated waves above the coral canopy.

In the home aquarium, Black Axil Chromis are among the easiest marine fish to keep. They are hardy, disease-resistant, and accept virtually any prepared food. A group of five to seven individuals in a tank of 55 gallons or more creates a stunning display of natural schooling behavior. They are completely reef-safe and their peaceful temperament makes them compatible with nearly all community reef fish. Like other Chromis species, they may develop a dominance hierarchy in small groups, so keeping larger numbers helps distribute any mild aggression.