The Goldbelly cardinalfish Ostorhinchus apogonidesis also known as the Plain cardinalfish and the Short tooth cardinalfish . They are one of the few species of saltwater fish that are mouth brooders. They were formerly classified as Apogon apogonides but have now been reclassified as Ostorhinchus apogonides.
The Goldbelly Cardinalfish has proportionally large eyes and have two dorsal fins. The dorsal and caudal fins are translucent with a mauve tint. Their back and caudal area is a light mauve colour and the belly is a golden colour. Two light blue stripes run across the eye and the lines fade into darker blue dots.
IN THE WILD
During the day the Goldbelly cardinalfish will usually be found around an over hang or in a cave. During the day they form large aggregations particularly in the deeper water. At night they are usually solitary or very occasionally in pairs. Occasionally they will be seen in the spines of urchins but they prefer over hangs and caves. They are nocturnal feeders and are seen out in the open on night dives in Tanzanian waters mainly in the deeper waters from 18 meters downwards.
The Goldbelly cardinalfish is found across the Indian ocean and in the west Pacific. They are found between depths of 1-40 meters but seem to only occur in large numbers in deeper water.
The Goldbelly cardinalfish are nocturnal feeders , feeding mainly on zooplankton and small benthic organisms.
During breeding pairs are formed and after performing a mating dance, the eggs are laid by the female and fertilized by the male. The male then collects the fertilized eggs and carries the eggs in his mouth until they hatch. During this time the male cannot feed. Towards the end of the incubation period the males become quite skinny making the protruding mouth more noticeable. This can result in cannibalism with the male eating some of the eggs.
Goldbelly cardinals are peaceful fish and prefer being in small groups. Being nocturnal feeders they are slightly reclusive during the day. They will eat small crustaceans and therefore are not technically reef safe. Some cardinalfish have been bred in captivity by breeders such as Orafarm where they are occasionally available.
Purchasing captive bred fish takes the pressure off of wild populations and if one can do so one should.