Iris Rainbowfish

Melanotaenia iris is a relatively small and delicately built rainbowfish from the Fly River system in Papua New Guinea. The species is particularly notable for its extraordinary iridescence — the body scales shift through blue, green, gold, and purple depending on the viewing angle and light source, producing an almost holographic shimmer that few other freshwater species can match. Males develop the most intense iridescence and carry deep red-orange accents in their finnage.

This species is reasonably adaptable and can be maintained in a standard rainbowfish community aquarium. It prefers slightly alkaline, moderately hard water but tolerates moderate variation. Because of its smaller size compared to many Melanotaenia, it works well in 80-litre aquariums and pairs nicely with blue-eyes, smaller tetras, and other peaceful nano-to-medium community fish.

Iris Rainbowfish have a typical rainbowfish breeding strategy, depositing adhesive eggs on fine-leaved plants. They are not demanding to spawn but the fry are small and require appropriately sized food for the first few weeks. The species is not commonly seen in general retail but is available from specialist suppliers.

Water: pH 7.0–8.0, temperature 22–28°C, moderately hard; perform regular weekly water changes of 25–30%. Tank: Minimum 80 L; planted aquarium with open midwater space; gentle to moderate current preferred. Feeding: Quality fine flake, micro-pellets; live and frozen small invertebrates to bring out best colour. Breeding: Egg scatterer on fine plants or spawning mops; fry are small and need infusoria or commercial fry food first. Compatibility: Excellent community fish; suitable with blue-eyes, small tetras, and other peaceful species.