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.


Lake Kutubu Rainbowfish
Lake Kutubu Rainbowfish
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℃


In the home aquarium, the Lake Kutubu Rainbowfish will readily accept most good quality dried foods such as granules, flakes and sinking pellets. These modern food products have been developed to provide all adequate nutrition to maintain your fish's health and dietary requirements.

Providing additional foodstuffs such as live, frozen, and freeze-dried meals such as bloodworm, daphnia, and tubifex once or twice a week will provide additional benefits to your fish's health and well-being but is not a must for this fish.

It should be noted that bloodworms should only be given as an occasional treat and should not be used as the staple diet as they are difficult for fish to digest and can potentially cause blockages.

This fish is an omnivore in the wild, meaning it will consume some vegetable matter. Although most modern fish foods take this into account and include them in their products, you can still supplement your fish's diet with blanched vegetables such as spinach, broccoli, and zucchini. Ensure you do not overfeed your fish and remove any leftovers the following day.

Sexual Dimorphism

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.


Breeding the Lake Kutubu Rainbowfish is straightforward once these fish are happily established and settled into your aquarium. You will need a mature pair or group of males and females, along with a spawning mop, preferably floating at the top of the aquarium downwards to the substrate.

Despite spawning year-round, Rainbowfish lay many eggs at the beginning of the rainy season. In addition, temperature increases, and live and frozen foods often encourage spawning.

Check your spawning mops daily for any eggs that have been deposited and either remove the eggs from the mop or, better still, remove the entire mop to avoid contamination of the Rainbowfish eggs.

Tip: Have several spawning mops at hand so you can place a fresh spawning mop into the aquarium while you wait for the eggs to hatch on the other mop/s.

Place the spawning mop with eggs still attached into a separate small cycled aquarium with a sponge filter for flow, and add a few drops of Methylene Blue (Methylene Blue helps prevent fungal infections of eggs).

Your rainbowfish Eggs will hatch within 7 to 18 days, depending on the species and the temperature. We recommend 27°C = 80.6°F for the fastest development of fry.

Once the Rainbowfish fry hatch, they absorb their yolk sacs quickly and become free swimming, moving towards the water's surface. Once the fry reaches the water's surface, you can start feeding. We recommend feeding on Micorworm (the most straightforward live food to culture) and decapsulated brine shrimp egg powder several times a day while being careful not to overfeed and pollute the water column.

After a week or two, you can start to add newly hatched brine shrimp, but this isn't necessary to achieve a high success rate in our experience.

Rainbowfish fry grows slowly, so you should expect to wait several months before the fry is large enough to be added to the adult colony.

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: 12/08/2022 12:41:12