Van Heurni's Rainbowfish

Melanotaenia vanheurni is a rainbowfish from the Lakes Plains region of West Papua — a vast, seasonally flooded lowland of extraordinary biodiversity. Males develop a golden-olive to bronze body overlaid with iridescent scale-edge markings that shift between blue-green and gold depending on light angle, and the unpaired fins carry vivid red to red-orange colouration that deepens considerably as males approach dominance and breeding condition.

This species is adapted to the warm, slightly soft to moderately hard, slightly acidic to neutral waters of its lowland swamp and river habitat. It is rarely available commercially but maintained by a small number of dedicated hobbyist breeders, particularly in Europe and Australia. Care is not especially demanding, but the specific water parameters of its habitat should be respected for long-term health.

Melanotaenia vanheurni breeds in the typical Melanotaenia manner and produces moderate spawns on fine-leaved plants or spawning mops. Its rarity in the hobby means that hobbyists maintaining it should document their stock and cooperate with the wider rainbowfish community to maintain genetic diversity.

Water: pH 6.5–7.5, temperature 23–28°C, soft to moderately hard; stable, clean conditions important. Tank: Minimum 150 L; planted aquarium with open swimming space; gentle to moderate current. Feeding: Quality flake and pellets; live and frozen invertebrates regularly to develop red finnage. Breeding: Egg scatterer on fine plants; document and share breeding stock within the hobby community. Compatibility: Peaceful community species; compatible with other calm, similarly sized rainbowfish.