Rainbowfish

Adults reach up to 7 cm in length. Their coloration is mainly silvery, with dark horizontal stripes running across the body. Populations from different regions show minor colour variations: some have red fins, others yellow. Females are usually larger than males but their colours are less vivid.

These fish are naturally found in Papua New Guinea and Australia. They inhabit various biotopes, from turbid swampy waters to clear rivers and lakes. They prefer to stay among dense vegetation and near submerged branches and fallen trees.

The rainbowfish has a calm, peaceful temperament and gets along well with other species of similar size and disposition. Keep them in a school of at least 6–8 individuals of both sexes.

A group of 6–7 fish needs a tank of at least 60 litres. The decor can be anything, but include both densely planted areas and open swimming space. Maintaining high water quality is essential. Install an effective filter and change 15–20% of the water weekly. Choose a filter that does not create strong flow, as this species is not adapted to powerful currents. Otherwise the fish are undemanding and do well across a wide range of water chemistry and temperature.

These undemanding, omnivorous fish accept dried, frozen and meat foods readily. Offer meat foods at least once a week; this keeps them in good condition and brings out brighter colours.

While keeping these fish is straightforward, raising the fry can be challenging. For successful spawning and breeding, use moderately alkaline water (pH 7.5) of moderate hardness, maintain temperatures of 26–29°C, and feed quality foods regularly. In the breeding tank, provide dense plantings of fine-leaved plants or mosses; the female will lay eggs among them. Spawning takes about two weeks. One male can fertilise eggs from several females. These fish show no parental care, but adults usually do not eat eggs and fry — other tank mates may. Move the eggs to a separate rearing tank with the same water parameters as the main tank, fitted with a simple sponge-filter air lift, a light and a heater. Live or artificial plants are also helpful. The incubation period is 7–12 days. Newly hatched fry feed on yolk-sac reserves, then need infusorians and other microscopic food. As they grow, offer brine shrimp nauplii and other appropriately sized foods. Most of the time these fish stay near the surface, so sinking foods will not be eaten and will only foul the water.

Health problems usually arise from injury or unsuitable conditions that weaken the immune system and trigger disease. When illness appears, the first step is to check water parameters for harmful levels of toxic substances such as nitrates, nitrites and ammonia. Once the water is corrected, treatment can begin.

When selecting fish, look for activity: healthy rainbowfish are mobile and show interest in their surroundings. Avoid fish with visible damage to scales, coating, sores or unnatural belly swelling. Check that fins are intact with no signs of decay or white spots. Buy only active fish that school together; examine each fish carefully for parasites and signs of infection; choose fish with bright, saturated colours typical of the species; make sure there are no dead fish in the seller's tank, as this indicates poor maintenance.