Courtship behaviour has been observed in Hong Kong waters in April and June.
Males brood eggs by holding them in the mouth. Nocturnal feeding reported elsewhere, however, mouthbrooding males show no feeding activities at night. On the day of hatching, males release hatched larvae after sunset, suspected to link to the relatively low predation risk at night and convenience for parental males to resume feeding sooner after release.
Feeds on small crustaceans and fish.
The genus of this species has been changed, which was Apogon niger, so the scientific name used here, Apogonichthyoides niger, may be different from other Hong Kong field guides.
Body colouration varies from dark brown to light olive , sometimes even yellow.
Vertical dark bars visible on body in some colour variations, just as pale brown.