Max Size: 12.5cm

Lake Kutubu Rainbowfish (Melanotaenia lacustris)

The Lake Kutubu Rainbowfish is very peaceful but can disturb slow-moving or smaller fish with its relatively large size and rapid movements. These Rainbowfish can be pretty skittish and will do far better when kept in a shoal of at least 6 to 8 individuals, preferably more. The males will be encouraged to display their best colours in the company of their own kind. Remember, you will need a suitably sized aquarium if you plan on keeping a large group.

Ideal tankmates for these Rainbowfish include other species of similarly-sized Rainbowfish, Barbs, Danios, Catfish such as Corydoras and Gobies. You can also keep these Rainbowfish with many Rift Lake Cichlids species as their water requirements are the same as the Lake Kutubu Rainbowfish.

Lake Kutubu Rainbowfish are playful and boisterous by nature; however, these behaviours can quickly turn into aggression and violence with badly chosen tank mates.

The Lake Kutubu Rainbow fish's body is extended, and it deepens as the fish ages. The head indents into a narrow triangular head. They have big eyes and paired dorsal fins. These fish are usually teal to cobalt blue on top and fade into a green colour. They display a silvery or yellowish colour on the bottom. This fish ordinarily has a thin cobalt blue stripe starting from the tail that disappears when it reaches the middle of the body.

Quick Facts
Scientific NameMelanotaenia lacustris
Other NamesTurquoise Rainbowfish, Blue Rainbowfish
OriginsPapua New Guinea
Aquarium LevelMiddle
Best kept asGroups 6+
Lifespan5 - 8 years
Water Parameters
Water TypeFreshwater
PH7.0 - 8.5
GH8 - 25
70 - 79℉
21.1 - 26.1℃

Photos of the Lake Kutubu Rainbowfish

Lake Kutubu Rainbowfish
Lake Kutubu Rainbowfish

Natural Habitat

Lake Kutubu Rainbowfish are endemic to Lake Kutubu in the Kikori River system in Papua New Guinea in Oceania. They inhabit very clear, still waters with submerged logs and roots and plenty of aquatic vegetation where they assemble in groups to feed on algae, insect larvae and small crustaceans.

Every two years, a strange thing happens at Lake Kutubu; an up-flow of dark water rises from the lake's bottom, causing the water to become oxygen-deficient, killing and reducing this Rainbow fish's population. This has now lead to the Rainbowfish being a cause for concern and endangered them.

What to feed the Lake Kutubu Rainbowfish

Lake Kutubu Rainbowfish are unfussy and will accept most foods offered to them. However, it would be best to feed these Rainbowfish a balanced diet of good quality dried food like pellets or flakes alongside frozen and live foods such as bloodworm, brine shrimp and tubifex. Regular feedings of both will help your fish to exhibit their best condition and colours. It would be more beneficial to feed your fish 2 to 3 times a day, remembering only to provide them with what they can consume in 5 minutes or less.

How to sex the Lake Kutubu Rainbowfish

It is relatively straightforward to distinguish male from female Lake Kutubu Rainbowfish. Males are slightly larger, have more arched backs and will be much brighter in colour. They also develop a broader body than females as they grow and can be more aggressive.

How to breed the Lake Kutubu Rainbowfish

It would be better to set up a separate breeding tank containing soft acidic water, a sponge filter, and, most importantly, numerous fine-leaved plants. A spawning mop or two will work just as well.

A group of Lake Kutubu Rainbowfish, in a two female to three male ratios, should be introduced into the breeding tank. It would be best if you conditioned them with live and plant-based foods. Remember, you are trying to emulate the flood season's bounty so feed more and higher quality food than you usually would.

Once the female has produced eggs, the males will display a fantastic show of intense colours and then direct the female to the spawning site, spawn, and rest. The spawning mop or plants should be removed and replaced after the spawning, or the parents will eat the eggs. The fish will repeat this daily for several days, with regularly decreasing numbers of eggs produced. It would be better to remove the parents when egg numbers fall or if the females start to show signs of fatigue.

About 7 to 12 days later, depending on the temperature, the eggs will hatch into fry. You will need to give the fry infusoria or liquid fry food until they are big enough to eat small live foods. The fry is quite challenging to raise until they reach around two months old.

Other Rainbowfish of interest

Banded Rainbowfish(Melanotaenia trifasciata)
Boesemans Rainbowfish(Melanotaenia Boesemani)
Celebes Rainbowfish(Marosatherina ladigesi)
Dwarf Neon Rainbowfish(Melanotaenia praecox)
Forktail Blue Eye Rainbowfish(Pseudomugil furcatus)
Honey Blue Eye Rainbowfish(Pseudomugil Mellis)
View all Rainbowfish
Date Added: 25/03/2021 - Updated: 02/02/2022 16:30:39