Spotted Blue Eye Rainbow "Aru IV"

Spotted Blue Eye Rainbow "Aru IV" (Pseudomugil gertrudae ‘Aru IV’) is one of the most captivating nano fish available for the planted aquarium. The Aru IV locality form is the most widely kept Spotted Blue Eye, displaying a warm golden-yellow body with vivid golden-yellow fin extensions that have been selectively developed through captive breeding to show unusually elongated, dramatic streamer fins. Despite their tiny size, male Spotted Blue Eyes are among the most spectacular display fish in freshwater fishkeeping — the constant fin-fanning courtship display is mesmerizing to watch.

Feeding & Care Tip: Sera Vipan Baby is the ideal daily staple for this tiny species — crush lightly before feeding. Supplement 2–3× per week with Hikari Frozen or Freeze-Dried Baby Brine Shrimp, which are a perfect size for this fish. Feed small amounts 2–3 times daily. Competition at feeding time can be intense — ensure all fish receive adequate food.

Native to Aru IV locality, Aru Islands, Indonesia. This species inhabits slow-moving, heavily vegetated streams, billabongs, and swamps. Some populations occur in very soft, acidic blackwater while others are found in neutral water — the aquarium trade stock is generally adaptable to soft to medium, slightly acidic to neutral conditions.

Keep in groups of at least eight with a mix of males and females. Male display behavior is most active and spectacular in a mixed-sex group — males fan their elaborate fins continuously in competition for female attention. Keep only with other very small, peaceful species that will not outcompete them for food.

Blue-eye rainbowfish are best kept in a densely planted aquarium with fine-leaved plants and gentle filtration — strong currents will exhaust these small fish. They are most spectacular in natural-toned setups with dark substrate where the iridescent fin extensions and vivid eye color catch the light. Keep only with other small, peaceful species. Larger or more boisterous tankmates will outcompete them for food and space.

Care & Ideal Parameters