Threadfin Rainbowfish (Iriatherina werneri)

Iriatherina werneri, the Threadfin Rainbowfish, is an extraordinary nano fish from slow-flowing, densely vegetated habitats of New Guinea and northern Australia. Males bear spectacular thread-like extensions on their dorsal and anal fins and display vivid iridescent coloration when performing elaborate courtship displays with fans fully spread. A delicate but rewarding species requiring pristine, soft water and gentle filtration in a heavily planted tank with low current.

Keep in groups of 8 or more with at least two females per male. Provide a heavily planted nano or species tank with very gentle filtration (sponge filter) and minimal current. Soft, slightly acidic water is essential — use RO water or peat filtration. Feed micro-foods: baby brine shrimp, micro-worms, Cyclops, and quality nano flake. Avoid larger or active tank mates that will stress or outcompete this delicate species.