Lake Kutubu rainbowfish

Aquarium fish: Lake Kutubu rainbowfish (Melanotaenia lacustris)
Size: 12 cm
Origin: New Guinea
Water temperature: 20-25 ° C
Aquarium volume: 110 l

Lake Kutubu rainbowfish (Melanotaenia lacustris) – freshwater aquarium fish of the rainbow family. Also called the Rainbow of Kutubu.


The blue rainbow fish comes from New Guinea. It is an endemic species, ie it occurs only in the Kutubu lake in the Nowogwinejska Upland.

Characteristics and disposition

These fish are 12 cm long.

Adults have a green or blue back and a light belly. Males are slightly brighter in color, have a taller body and more elongated fins, usually slightly darker than females. Lake Kutubu rainbowfish fish are quite skittish fish. They feel good in a large group. You should keep at least 6-8 animals in the aquarium , but more are recommended.

Males in their company display the most beautiful colors and interesting behavior.

Nutrition and feeding

Like most rainbow fish, they are not picky eaters. They can be given dry, frozen and live foods. Regular feeding of the latter will ensure the best condition and intensive coloration of the fish.


They require a long aquarium of min.

120 cm , densely planted with plants to provide them with plenty of space for swimming and at the same time sufficient shelter. Other decorations are not really needed. When choosing plants for an aquarium with blue rainbow fish, it is worth remembering that they grow in the water in which these fish feel best, i.e. slightly hard and alkaline. The movement of water in the tank should be minimal.

The species is gentle, but their high activity may disturb smaller and slow-swimming fish. Good company will be other similarly sized rainbow, tetras, zebrafish, barbs, freshwater plantain and cuirass. Due to their preferences regarding water parameters , they can be kept with many species of cichlids from Lake Malawi or Tanganyika .


Kutubu rainbow fish are spawning fish. Breeding them is not difficult, but rearing fry may be a bit difficult for beginner aquarists.

The spawning tank should have min. 75 cm long. Water, preferably medium hard, alkaline with a pH of 7.5 and a temperature of approx. 23-24 ° C. A small sponge filter is sufficient for filtration.

The aquarium should be filled with lots of small-leaved vegetation, e.g. java moss. Alternatively, you can use an artificial aquarium mop. We feed the adult fish abundantly with frozen and live food until they are ready for breeding. When the females are definitely thicker and the males are more vividly colored, we choose the thickest female and the largest, most beautifully colored male and move it to the previously prepared aquarium.

A slight increase in temperature stimulates the fish to spawn. The female spreads the eggs every day for several days. The eggs are attached to the surface of plants or the ground with thin filaments. Adult individuals will eat eggs and fry as soon as the opportunity presents itself. Therefore, it is best to check the spawning tank daily and transfer any spawning grains you notice to a separate aquarium.

Depending on the water temperature, the eggs hatch within 7-12 days. The larvae in the first week need micro foods. Then they can be fed e.g. with artemia. Due to the fact that the fry have a tendency to swim near the water surface, foods that sink to the bottom are not recommended.


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