Sphaeramia orbicularis Breeding Guide

The orbiculate cardinalfish Sphaeramia orbicularis is a paternal mouthbrooder: the male incubates up to about 12,000 eggs for roughly 8 days. This guide covers sexing, conditioning, spawning and mouthbrooding.

Overview

Sphaeramia orbicularis, the orbiculate cardinalfish, is a member of the family Apogonidae reaching about 10 cm total length, with a common length near 8.9 cm. It occurs throughout much of the Indo-Pacific from East Africa to Kiribati, north to the Ryukyu Islands and south to New Caledonia, at depths of 0 to 5 m, often in mangrove and estuarine shallows. It feeds mainly on planktonic crustaceans at night. The species is a paternal mouthbrooder, making it one of the more accessible marine fishes for captive reproduction.

Sexing

Mature males of cardinalfishes have a larger jaw and longer head that accommodates the egg mass during incubation, which is the most reliable distinguishing feature. According to FishBase, males of this species reach sexual maturity at about 7 cm and females at about 6 cm. Outside the breeding period the sexes are otherwise similar in coloration.

Conditioning

Adults condition well on a varied carnivorous diet reflecting their natural intake of planktonic crustaceans, fed in the evening to match their nocturnal feeding habit. Keeping a small group lets a compatible pair form naturally. The species tolerates the lower-salinity conditions of its mangrove and estuarine habitat, but stable, mature water best supports spawning.

Spawning Behavior & Trigger

Courtship and spawning occur on a semi-lunar cycle, shortly before the full and new moons. After pairing, the female releases eggs that the male takes into his mouth and fertilises, forming a cohesive egg mass. FishBase reports that males incubate up to about 12,000 eggs.

Egg & Fry Care

The male broods the egg mass in his mouth for about 8 days, during which he does not feed; many cardinalfishes show breeding-specific male jaw coloration that helps conceal the eggs. The larval phase is pelagic, and after settlement juveniles grow at roughly 3 to 6 mm per month. Rearing the planktonic larvae requires small live first foods, so a dedicated larval system separate from the display is needed for grow-out.

Common Challenges

The main difficulties are protecting the brooding male from harassment so he does not prematurely release or swallow the eggs, and rearing the small pelagic larvae through their first-food stage. Because the larvae are planktonic rather than the larger, advanced young of some other cardinalfishes, larval feeding is the principal bottleneck.