Boeseman's Rainbowfish

Adult Boeseman's Rainbowfish reach 8–11 cm in length. Their colour is quite variable: the head and front of the body are blue, gradually shifting to yellow-orange tones towards the tail and on the tail itself. Males are usually larger and display more intense, vivid colours.

This species occurs naturally only in the western tip of New Guinea, now part of Indonesia. In the wild it is found in three small lakes and their tributaries. It prefers shallow areas with abundant aquatic vegetation. Unfortunately, the species is endangered in nature. Most fish sold in shops are farm-bred.

Boeseman's Rainbowfish are peaceful and active. They get along well with other fish of similar size and temperament that share the same requirements. Keep them in a group, preferably 6–8 individuals of both sexes. Interestingly, males display more vivid colour when they have rivals.

A school of Boeseman's Rainbowfish needs a tank of at least 110 L with a low water level. The setup can be simple: plant dense stands of rooted and floating plants while leaving plenty of open swimming space. Other décor is optional. These fish come from still waters, so avoid excessive water movement. Set up your filter for moderate circulation.

Boeseman's Rainbowfish are not fussy eaters and readily take all common foods: dry, live and frozen. The quality and composition of the diet directly affect the brightness of their colour. Use food from reputable makers, and offer live foods such as Artemia or bloodworm at least once a week.

Successful breeding requires hard, slightly alkaline water (pH around 7.5) at 27–29°C and a protein-rich diet. Provide fine-leaved or low plants, or their artificial substitutes. Spawning lasts about 2 weeks; the female lays a few eggs daily among plants, attaching them to leaf surfaces with sticky threads. One male can fertilize eggs from several females. These fish show no parental care and ignore their eggs and fry after spawning, but they do not eat them either. Tank mates, however, may consume the fry and eggs. To protect the brood, carefully move the eggs to a separate tank with identical water parameters. The incubation period lasts 7–12 days. In the first days after hatching, fry need infusoria. From the first week onwards, you can offer powdered fry food and/or Artemia nauplii.

Health problems arise only from injury or poor conditions, which weaken immunity and trigger disease. If the fish show symptoms, first test the water for any unusual levels or dangerous concentrations of toxins such as nitrite, nitrate or ammonia. Once you find any deviation, restore all parameters to normal before treating the fish.

When buying Boeseman's Rainbowfish, note that young fish in the shop often look grey and drab—this is normal for the species. Bright colour develops only as they mature with good food and stable conditions. Avoid fish with damage, ulcers or odd behaviour. Choose active individuals that show interest in food and school together. Since this is a schooling species, buy 6–8 fish at once to reduce stress and support normal socialisation. Make sure the seller's tank shows no signs of infectious disease, as rainbowfish are sensitive to environmental conditions.