Threadfin Cardinalfish

Geographical Origin and Habitat: Tropical Indo-Pacific: from the Red Sea and East African coast to Samoa, north to the Ryukyu Islands. Inhabits sheltered coral reefs and lagoons, forming dense schools among branching corals (Acropora) at depths of 1 to 12 meters.

Taxonomy and Morphology: Member of the family Apogonidae. Features a translucent, laterally compressed body, large eyes ringed in bright blue, and a long filamentous ray on the first dorsal fin. Grows up to 6 cm.

Social Behavior: Extremely peaceful and schooling. It is one of the few marine species that forms true tight schools swimming in unison near reef branches.

Coloration and Sexual Dimorphism: Semi-translucent body showing the spine, characterized by iridescent blue and golden hues with thin vertical orange lines. Cobalt blue eyes. Dimorphism is absent.

Aquarium Setup: Requires a tank of at least 80 liters (larger preferred for schools). Provide branching Acropora corals or vertical shelters. Low jumping risk.

Diet and Feeding: Planctivorous carnivore. In captivity, feeds on fine frozen foods like brine shrimp, mysis, copepods, and lobster eggs. Feed twice daily.

Water Quality: Keep parameters stable. Temperature 24-27°C, pH 8.1-8.4, salinity SG 1.020-1.026. GH 15-25. Prefers gentle to moderate water flow.

Compatibility and Cohabitation: 100% reef safe. Ideal for quiet community marine tanks with branching corals. Do not house with fast or aggressive fish that may intimidate it.

Aquarium Breeding: Paternal mouthbrooder. The male holds the egg mass in his mouth until hatching. Captive spawning is difficult to raise.

Risks and Diseases: Susceptible to skin parasites if stressed by aggressive tankmates. May waste away if not fed enough due to food competition.