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Encyclopedia / Rainbowfish / Lake Kutubu rainbowfish
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Lake Kutubu rainbowfish

Melanotaenia lacustris · Turquoise rainbowfish, Kutubu rainbow, Lacustris

Peaceful, active schooling fish; keep a group of 6 or more with other peaceful fish in a long tank.

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12 cmBody length, without tail ✓
20–25 °CTemperature ✓
7–8pH ✓
108 LSmallest tank ✓
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Tank mates
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Not recommended
  • They need different temperatures (20–25 °C vs 26–30 °C). No setting suits both.
  • Only a narrow pH range suits both: exactly 7.
Not recommended
  • Oscar eats animals up to about 12 cm. Lake Kutubu rainbowfish only grows to 12 cm.
Not recommended
  • They need different temperatures (20–25 °C vs 27–30 °C). No setting suits both.
  • Only a narrow pH range suits both: exactly 7.
With conditions
  • Only a narrow pH range suits both: exactly 7.
With conditions
  • Only a narrow pH range suits both: exactly 7.
Compatible
Compatible
Compatible
Compatible
Compatible

264 species in our list are a good match.

Facts checked against sources on 16 Oct 2026. ✓ means a source backs it; ? means no reliable source yet. See sources

Care and water

Hardness ✓10–20 dGH
Group size ✓6 or more
Temperament ✓Peaceful
Swims at ?Top
Care level ✓Easy
Diet Omnivore
Lifespan ?Unknown
Size in shops 5–8 cm
Growth Medium

Behavior

Peaceful, active schooling fish; keep a group of 6 or more with other peaceful fish in a long tank.

Food

Flakes, micro pellets, frozen foods and small live foods.

Tap a food to see what it is.

Male or female

Mature males are larger, brighter and much deeper-bodied than females; conditioned males show an orange patch above the gill cover.

Health

Common problems. Tap one to see the signs. This is a guide, not a diagnosis.

Breeding

Egg-scatterer (spawning mops) · Easy

Egg scatterer: a pair spawns daily for several weeks into fine-leaved plants or mops, attaching eggs by threads. Adults tend to eat the eggs, so move eggs to a rearing tank. Fry need infusoria first and stay near the surface.

Pairing

A group of 6 or more; let them pair.

Setup

A 100 L planted tank with spawning mops and good water flow.

What starts it

Warm water, plenty of live food and regular water changes.

Eggs

Batches of eggs daily for several weeks; eggs hatch in 7-12 days depending on temperature.

Raising the fry

Feed infusoria, then baby brine shrimp and microworms.

Common mistakes
  • Keeping too few fish so spawning does not start
  • Eggs eaten by adults
  • Cold or dirty water
Full breeding guide, day-by-day plan and simulator →

Where it lives in the wild

RegionLake Kutubu, Southern Highlands of Papua New Guinea
Rivers and lakesLake Kutubu and its outlet, the Soro River (Kikori basin)
HabitatClear, plant-rich shallows of a highland limestone lake
Native rangeAbout 30 km across
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The story of the lake kutubu rainbowfish

A blue-turquoise rainbowfish found only in Lake Kutubu, Papua New Guinea. It is listed as Endangered by IUCN (assessed 2019); the lake is threatened by overfishing, partly for the aquarium trade, and oil development. Full colour can take over a year.

Ian Munro described this rainbowfish in 1964 from Lake Kutubu, a remote lake in Papua New Guinea's Southern Highlands. Its turquoise-blue colour and adaptable nature made captive-bred fish a hobby favourite. The lake is home to several fishes found nowhere else.

First described by Ian S. R. Munro in 1964. Named for 'lacustris' means 'of the lake', for Lake Kutubu.

  • In the wild it is known only from Lake Kutubu and its outflow.
  • Lake Kutubu has a remarkable number of endemic fish species for its size.
  • Its blue shade can shift with mood and light, often with a darker belly stripe.

Sources

15 facts checked with sources