Crossing Rainbowfish Care Guide - Aquarium Setup, Diet & Breeding

Crossing Rainbowfish are colourful, active hybrids created from two closely related groups of Australasian rainbowfish. Their exact appearance varies according to the parent strains involved, but they commonly display a deep-bodied profile, large reflective scales and a vivid blend of blue, green, gold, orange or red tones.

Males generally develop the strongest colour, particularly when mature or displaying to females. They may intensify their markings during courtship, while females and younger fish are often slimmer and less brightly coloured. Because this is a hybrid rather than a standard wild species, colour patterns and body shape can differ considerably between individuals.

These rainbowfish are energetic open-water swimmers with a peaceful but lively temperament. They are social fish that spend much of their time cruising through the middle and upper levels of the aquarium, with males frequently displaying alongside one another without causing serious harm.

The parent genera include species from clear streams, rivers, floodplain waters and other well-oxygenated freshwater environments across Australia and New Guinea. Crossing Rainbowfish are a product of aquarium breeding and are usually kept for their attractive combination of rainbowfish colour, activity and hardiness.

Crossing Rainbowfish are captive-produced hybrids resulting from a cross between fish in the Melanotaenia and Glossolepis genera. Their parent species are native to freshwater habitats in Australia and New Guinea, so this hybrid does not have a single natural geographic range.

A group should have an aquarium of at least 120 litres, with a footprint of approximately 120 cm long by 40 cm wide; a longer tank is preferable because these are active swimmers. Provide open swimming space through the centre, sturdy filtration and good water movement, while using plants, wood or rocks around the sides and back for cover. A dark, fine-grained or smooth substrate can enhance their colours, and a secure lid is advisable because rainbowfish can jump.

Up to about 12.5 cm (5 inches) in length. Males are often deeper-bodied and may reach slightly greater overall size than females, although hybrid growth is variable.

Crossing Rainbowfish are omnivores and thrive on a varied diet. Offer a quality small pellet or flake as a staple, supplemented with frozen or live foods such as brine shrimp, daphnia, bloodworm and mosquito larvae. Small portions of soft vegetable matter or spirulina-based foods can also be included. Feed modest amounts once or twice daily, giving enough for the group to consume promptly.

Crossing Rainbowfish suit peaceful community aquariums containing other similarly sized, active fish. Suitable companions include larger tetras, peaceful barbs, danios, rasboras, Corydoras, peaceful loaches and other appropriately sized rainbowfish. Avoid very slow or timid species that may be outcompeted at feeding time, as well as aggressive cichlids, fin-nipping fish and much smaller fish that could be harassed or swallowed. Keeping a group helps spread social attention and produces more natural behaviour.

Crossing Rainbowfish are egg-scattering spawners. Condition a group with generous amounts of high-quality live or frozen food, then provide spawning mops or fine-leaved plants for the eggs to attach to. Spawning usually takes place over several days, with the adults likely to eat the eggs if given access to them. Move the mop to a separate, gently filtered hatching container and raise the tiny fry on infusoria or a suitably fine first food before progressing to newly hatched brine shrimp. As this is an intergeneric hybrid, fertility and the appearance of offspring can be unpredictable, and some individuals or pairings may be sterile.

Mature males are usually more intensely coloured, deeper-bodied and larger-finned than females, especially when displaying. Females tend to be slimmer and less vividly marked, though the degree of difference varies between hybrid lines.