Ornate Rainbowfish

Rhadinocentrus ornatus is a small, graceful rainbowfish from the coastal streams and wallum heath wetlands of south-east Queensland, Australia. It is the only species in the genus Rhadinocentrus and is notable for its preference for soft, acidic to neutral water — quite different from the alkaline preferences of most other Australian rainbowfish. Males are beautifully coloured with a body that shimmers with red, blue, and gold iridescence, and fine, delicate finnage.

This species is adapted to the soft, tea-coloured waters of heath wetland streams, where tannins from leaf litter lower the pH and soften the water. In the aquarium it thrives best in conditions that approximate this — soft, slightly acidic water, subdued lighting, and a dark substrate that reduces stress and enhances colouration. It is more demanding than most rainbowfish and not suitable for hard, alkaline tanks.

Rhadinocentrus ornatus is a Queensland endemic that has experienced some habitat loss and is not as common as it once was. It is well-established in the hobby among Australian native fish enthusiasts and can be sourced from specialist breeders. It breeds readily in soft, slightly acidic water among fine-leaved plants.

Water: pH 5.0–7.0, temperature 20–26°C, soft to slightly hard; acidic conditions preferred — use RO or rainwater if needed. Tank: Minimum 60 L; dark substrate, leaf litter, subdued lighting; planted with fine-leaved species. Feeding: Fine flake, micro-pellets; live micro-worms, daphnia, and brine shrimp nauplii for best colouration. Breeding: Egg scatterer on fine plants in soft, slightly acidic water; fry small and delicate at first. Compatibility: Best with other soft-water Australian natives or gentle nano species; incompatible with hard-water rainbowfish.