Gracilis Rainbowfish

Melanotaenia gracilis is one of the more slender and streamlined members of the genus, originating from the southern lowland river systems of Papua New Guinea. Its elongated, laterally compressed body is covered in scales that shimmer with blue-green iridescence, while the dorsal and anal fins carry attractive orange tips that brighten conspicuously during male rivalry displays. The species is well-suited to aquariums with a moderate to brisk current, mimicking its natural riverine habitat.

This species is appreciably hardy once established and adapts well to a range of water conditions as long as extremes are avoided. It is rarely seen in mainstream fish shops but occasionally appears through specialist importers and hobbyist breeders. Kept in groups of six or more, males develop their most intense colouration and engage in energetic but harmless lateral display contests.

Melanotaenia gracilis breeds in the typical rainbowfish manner, scattering adhesive eggs among fine-leaved vegetation. Conditioning fish with live and frozen foods prior to breeding attempts improves egg yield. Fry are moderately small and can be raised on infusoria and brine shrimp nauplii.

Water: pH 7.0–8.0, temperature 23–28°C, moderately hard; tolerant of a range of conditions once acclimated. Tank: Minimum 100 L; open swimming space with gentle current; plants at the margins provide security. Feeding: Omnivorous; accepts quality flake and pellets; live and frozen foods improve colouration and breeding condition. Breeding: Egg scatterer among fine vegetation; remove eggs or parents post-spawning for best survival rates. Compatibility: Peaceful with most community fish; keep with similarly sized, non-nippy species.