Blue Rainbowfish Care Guide - Aquarium Setup, Diet & Breeding

The Blue Rainbowfish is a striking, high-bodied species with shimmering blue to blue-green sides, a darker back and translucent fins often edged with warm orange or yellow. Mature males develop the strongest colour and a deeper body profile, especially when displaying to females or competing with other males.

Blue Rainbowfish are native to Lake Kutubu and nearby waterways in the Southern Highlands Province of Papua New Guinea, in Oceania. They inhabit clear, calm freshwater around the lake’s margins and connected streams.

A group of Blue Rainbowfish needs an aquarium of at least 200 litres, with a footprint around 120 cm long by 45 cm wide to provide adequate swimming space. Use an open central area for active movement, with hardy plants, smooth rocks, wood and some marginal cover around the sides and rear. A sand or fine-gravel substrate suits their natural surroundings, while a secure lid is advisable because rainbowfish can jump. Good filtration, strong oxygenation and regular maintenance are important for this active species.

Up to 12 cm (4.7 inches) in total length. Males are usually larger and deeper-bodied than females, while females more commonly remain around 8–10 cm (3.1–3.9 inches).

Blue Rainbowfish are omnivores and should receive a varied diet of quality flakes and small pellets supplemented with frozen or live foods such as daphnia, brine shrimp, mosquito larvae and bloodworm. Regular vegetable matter, including spirulina-based foods, is also beneficial. Feed small portions that they can finish promptly, as they are active surface and midwater feeders.

Blue Rainbowfish are generally peaceful but energetic community fish. Suitable companions include other robust rainbowfish, larger peaceful tetras, peaceful barbs, danios, Corydoras, peaceful loaches and similarly sized peaceful Lake Kutubu-compatible species. Avoid very small, slow-moving or long-finned fish that may be intimidated by their activity, as well as aggressive cichlids and fin-nipping tankmates.

Blue Rainbowfish are egg-scattering spawners that can be bred in a separate breeding aquarium. Provide fine-leaved plants or spawning mops for the adults to scatter their adhesive eggs among, then remove the mop or eggs to prevent them being eaten. Hatching usually takes around one to two weeks, depending on temperature. The tiny fry need infusoria or another suitably fine first food before progressing to baby brine shrimp and powdered foods.

Males develop brighter blue and turquoise colouring, a deeper body, more extended fins and a more pronounced mid-body profile than females. Females are typically smaller, slimmer and less intensely coloured, with more rounded, subdued fins.