Blue Reef Chromis Breeding Guide

Breeding Chromis cyaneus: a demersal nest spawner in which the male clears a substrate nest, the female lays adhesive eggs on it, and the male guards and aerates the clutch until pelagic larvae hatch.

Overview

Chromis cyaneus (recognised by FishBase under the current name Azurina cyanea) is a Western Atlantic damselfish of Bermuda, southern Florida and the Caribbean Sea, reaching about 15 cm. Adults congregate above deep outer reefs and feed on zooplankton, mainly copepods. FishBase records it as oviparous with distinct pairing during breeding, with demersal eggs that adhere to the substrate and male parental care. IUCN status is Least Concern.

Sexing

Like other Pomacentridae, this chromis shows little permanent external difference between the sexes outside the breeding season. Sex is most reliably inferred from spawning behaviour: the male establishes and tends a substrate nest, while the female is the partner that enters it to deposit eggs. Working from a group rather than a single chosen pair gives the best chance of a compatible male and female forming naturally.

Conditioning

A school held in spacious, stable reef conditions and fed several times a day on small zooplankton-type foods comes into condition. Because the wild diet is dominated by copepods, frequent feeding of fine planktonic and meaty foods supports egg production and reflects the natural feeding ecology recorded on FishBase.

Breeding Setup

A pomacentrid nest requires open, defensible substrate. The male clears an area of algae and invertebrates to create a nest site on hard substrate, so the breeding system should provide flat rock or a similar firm surface within a territory the male can defend. A roomy tank allows the school to function while a pair separates to spawn.

Spawning Behavior & Trigger

Damselfish engage in ritualised courtship displays such as rapid bursts of motion, chasing and wide fin extension. The male swims behind the female as she lays a string of sticky eggs that attach to the cleared substrate, and fertilises them externally. FishBase notes distinct pairing during breeding for this species.

Egg & Fry Care

The eggs are demersal and adhere to the substrate, and the male guards and aerates the clutch. Across Pomacentridae the eggs hatch in roughly two to seven days, releasing tiny larvae of about 2 to 4 mm that enter a pelagic stage lasting from about a week to over a month depending on species. These larvae require very small live planktonic foods such as cultured copepods.

Common Challenges

The principal obstacle is the pelagic larval phase: the larvae are minute and pelagic and demand a continuous supply of correctly sized live plankton, so rearing is generally restricted to specialist culture facilities rather than home tanks. Until species-specific larval protocols are published, home spawning typically ends at the planktonic stage.