Half-and-Half Chromis Breeding Guide

Breeding Chromis retrofasciata: a small Western Pacific demersal nest spawner that lives among branching coral, with the male tending the nest, the female laying adhesive eggs, and pelagic larvae after hatching.

Overview

Chromis retrofasciata (recorded by FishBase as Pycnochromis retrofasciatus) is a small Western Pacific damselfish from Indonesia to Fiji, reaching only about 6 cm standard length. It occurs singly or in small groups and stays close to thickly branching coral shelter in clear lagoon and seaward reefs. FishBase records it as oviparous with distinct pairing, demersal eggs adhering to the substrate, and male guarding and aeration. IUCN status is Least Concern.

Sexing

External sexual differences are slight, so the sexes are distinguished mainly by breeding behaviour. The male holds and tends a nest among or beside branching coral, while the female approaches to spawn. Because this species is comparatively peaceful and small, keeping several together allows a compatible male and female to associate.

Conditioning

Specimens kept in a stable reef with healthy branching coral and fed frequent small meals come into condition. As a small planktivore associated with coral cover, regular feedings of fine planktonic and meaty foods support egg production while the fish remains close to its shelter.

Breeding Setup

This species' close association with branching coral shapes the setup: the nest is sited on hard substrate near or within coral shelter that the male can clear and guard. Its small size makes it suited to compact reef systems, provided firm substrate for the nest is available within a defensible territory.

Spawning Behavior & Trigger

Following the pomacentrid pattern, courtship involves ritualised displays near the nest, after which the female lays a layer of sticky eggs onto the cleared substrate and the male fertilises them externally. FishBase records distinct pairing during breeding for this species.

Egg & Fry Care

The demersal eggs adhere to the substrate and are guarded and aerated by the male. In Pomacentridae generally the eggs hatch in about two to seven days, and the resulting larvae of roughly 2 to 4 mm pass through a pelagic stage of about a week to more than a month, feeding on very small live plankton such as cultured copepods.

Common Challenges

Despite this chromis being small and relatively peaceful, the pelagic larval phase remains the limiting factor, requiring continuous dense live plankton that home tanks rarely sustain. No species-specific larval rearing protocol is documented, so captive spawning generally ends at the planktonic stage.