Blue-Green Chromis (Chromis caerulea) Breeding Guide

Chromis caerulea belongs to the blue-green chromis (Chromis viridis) group, demersal nest spawners in which the male prepares and guards a nest shared by several females; eggs hatch in 2–3 days.

Overview

Chromis caerulea is a blue-green chromis closely associated with Chromis viridis (Cuvier, 1830); Wikipedia notes the two are sometimes considered conspecific. As the consulted sources treat this fish within the C. viridis blue-green chromis group, the breeding facts below are drawn from documented C. viridis biology, which is a demersal nest spawner reaching about 10 cm total length across the Indo-Pacific. FishBase classes it as oviparous with distinct pairing during breeding.

Sexing

Outside of spawning the species shows little external dimorphism. A practical cue documented for C. viridis is colour change during spawning: the male turns more yellowish in colour. Otherwise the nest-preparing, guarding individual is the male.

Conditioning

A detailed conditioning protocol is not documented, but C. viridis matures at about 5.8 cm. The fish is planktivorous (feeding on phytoplankton and zooplankton in the wild); a varied diet rich in 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 the species in a group, as it is a schooling fish.

Breeding Setup

Provide open sand or rubble adjacent to rock, mirroring the sand-and-rubble nesting surfaces used by C. viridis. A dominant male prepares a nest there, and the family pattern has the male clear the area of algae and invertebrates. Keeping a group increases the chance of a pair forming; this is one of the more peaceful damselfishes.

Spawning Behavior & Trigger

For C. viridis, the male prepares a nest on sand or rubble that is shared with several females, which deposit a large number of demersal eggs adhering to the substrate; the male fertilises and then tends them. Specific environmental triggers are not detailed in the consulted sources beyond the male's nest preparation and courtship colour change.

Egg & Fry Care

The male guards the nest and ventilates it with its fins, and removes unfertilised eggs to limit microbial contamination. The large number of eggs hatch in 2–3 days. Some aquarists have successfully bred the blue-green chromis in the home aquarium, though raising the planktonic larvae through settlement remains demanding.