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Glossolepis incisus

Red Rainbowfish

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Last revised 2026Edit this page

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Glossolepis incisus male
Glossolepis incisus maleJJPhoto

Quick factsEdit

Length
150mm SL6in SL
Tank base
120 × 30cm48 × 12in
Temp
24–29°C75–84°F
pH
7.0–8.0
Hardness
10–20dGH

Difficulty5 of 8 measures

Moderate

How the rating is worked out

Space
large tank
Water
needs a steady pH
Temp
flexible
Diet
unknown
Temperament
peaceful
Social
needs to be in a group
Compatibility
unknown

Other demands

Each of these can raise the rating on its own, whatever the measures above say.

Hardiness
unknown

The red rainbowfish, Glossolepis incisus, is a rainbowfish from the Lake Sentani region of northern New Guinea, Indonesia. Also known as the salmon-red or New Guinea rainbowfish, it is usually found in shoals around heavily vegetated areas. Mass-bred fish have far less colour than wild ones. It is quite skittish and does far better in a shoal of at least 6-8.

Distribution

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Indonesia, specifically the Lake Sentani region of Northern New Guinea. It's usually found in shoals around heavily vegetated areas. The lake is connected to the ocean by a small tributary and so contains an interesting mix of species.

The lake itself and surrounding waters.

Aquarium size

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Standard length
150mm SL6in SL
Aquarium base
120 × 30cm48 × 12in
Volume
~108litres~29US gal

An active swimmer, so the tank should be at least 120 ∗ 30 ∗ 30 cm48 ∗ 12 ∗ 12 in - ~108 litres~29 US gal.

Maintenance

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This species, like most rainbows, looks most at home in a planted aquarium. Provide areas of dense vegetation, along with some open areas for swimming. Water movement should be quite gentle.

Water conditions

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Temperature
24–29°C75–84°F
pH
7.0–8.0
Hardness
10–20dGH

Temperature: 24 – 29 °C75 – 84 °F

pH: 7.0-8.0. It will not do well in soft, acidic conditions.

Hardness: 10-20°H

These recommendations come from this profile’s own figures. They contain affiliate links, so we may earn a commission.

Unfussy and will accept most dried, frozen and live foods. Regular feedings of the latter two will ensure the best colouration.

Behaviour and compatibility

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Very peaceful but can disturb smaller or slow-moving fish with its rapid movements and relatively large size. Good tankmates include other similarly-sized rainbowfish, characins, danios, barbs, and catfish such as Corydoras.
The red rainbowfish is quite skittish and does far better when kept in a shoal of at least 6-8 fish, preferably more. The males will also be encouraged to display their best colours in the company of conspecifics. Obviously a suitably-sized aquarium would be required for a very large group.

Sexual dimorphism

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Mature males develop a much higher back than females as they grow. Also males are the only sex to develop the characteristic red colouration that gives this fish its common name. Interestingly, when kept at slightly lower temperature all males turn a red colour, whilst in warmer water only the dominant fish tend to do so.

Reproduction

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Quite easy. Egg scatterer. The breeding aquarium should be at least 30" long and contain slightly hard, alkaline water with a pH of around 7.5. A small air-powered filter will provide sufficient oxygenation and flow. The tank should be filled with fine-leaved plants such as java moss, or nylon spawning mops. No substrate is necessary.
The adult fish are best conditioned in a group in a separate aquarium with plenty of live and frozen foods. Select the fattest pair for spawning and introduce them to the spawning tank. A small raise in temperature can induce spawning.

The pair will spawn for a period of several weeks, laying a few eggs each day. These are attached to surfaces by a small thread. Although the adults tend not to eat the spawn, it's easier to raise the fry in a separate aquarium, so we recommend checking the plants or mops daily and removing any eggs you find to a raising tank containing water from the spawning tank.

The eggs hatch in 7-8 days and the tiny fry initially require infusoria-type food, before graduating onto microworm or brine shrimp nauplii after a week or so. They're quite sensitive to unfavourable water conditions and frequent small water changes are a must.

Notes

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Also known as the salmon-red or New Guinea rainbowfish, this is one of the most popular rainbows in the hobby. Unfortunately, the colouration of today's mass-bred specimens is not even close to the spectacular wild fish. If you can find wild specimens they are well worth it.

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