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Encyclopedia / Rainbowfish / Spotted blue-eye
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Variations

2 kinds · tap one for a closer look

Spotted blue-eye

Pseudomugil gertrudae · Gertrude's rainbowfish, Spotted blue eye, Gertrudae

Peaceful and shy; keep a group in a planted tank.

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4 cmBody length, without tail ✓
21–28 °CTemperature ✓
4.5–7.5pH ✓
40 LSmallest tank ✓
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Tank mates
Check your own mix →
Not recommended
  • Tinfoil barb eats animals up to about 5 cm. Spotted blue-eye only grows to 4 cm.
Not recommended
  • Giant gourami eats animals up to about 10 cm. Spotted blue-eye only grows to 4 cm.
Not recommended
  • Angelfish eats animals up to about 4 cm. Spotted blue-eye only grows to 4 cm.
With conditions
  • Only a narrow temperature range suits both: 21–22 °C.
With conditions
  • Only a narrow pH range suits both: exactly 7.5.
Compatible
Compatible
Compatible
Compatible
Compatible

381 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 ✓5–12 dGH
Group size ✓8 or more
Temperament ✓Peaceful
Swims at ?Top
Care level ✓Moderate
Diet Carnivore
Lifespan ✓2–4 years
Size in shops 2–3.5 cm
Growth Medium

Behavior

Peaceful and shy; keep a group in a planted tank.

Food

Baby brine shrimp, daphnia, microworms and fine flake.

Tap a food to see what it is.

Male or female

Males are more patterned and colourful, with extended dorsal and anal fins; females are duller and plainer.

Health

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

Breeding

Egg-scatterer (spawning mops) · Moderate

Egg scatterer with no parental care: eggs with sticky threads are laid a few at a time on plants or mops through the day, and adults eat eggs and fry. Breeds all year in the aquarium at 24-28 °C.

Pairing

A group of 6 or more.

Setup

A 30 L planted tank with spawning mops and floating plants.

What starts it

Warm water and live food.

Eggs

Usually 1-3 eggs at a time, up to about 10-12 per female per day; eggs hatch in about 4-10 days depending on temperature.

Raising the fry

Feed infusoria, then baby brine shrimp.

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

RegionAru Islands, southern New Guinea and northern Australia
Rivers and lakesAru Islands, Fly River region, Cape York and Arnhem Land streams
HabitatLily-filled swamps, lagoons and quiet streams
Native rangeAbout 1,200 km across
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The story of the spotted blue-eye

A tiny blue-eye from northern Australia, southern New Guinea and the Aru Islands, with dark-spotted fins and blue eyes. Wild populations differ in colour and fin shape, but most fish on sale are one commercially bred ornamental strain; locality fish (such as Aru forms) are kept by specialists.

Max Weber described the spotted blue-eye in 1911 from the Aru Islands. It is a tiny fish of quiet, weedy waters across southern New Guinea and northern Australia. Aquarists value it for its spotted, sail-like fins and suitability for small planted tanks.

First described by Max Weber in 1911. Named for Named after Gertrud Merton, wife of collector Hugo Merton.

  • It rarely exceeds 3–4 cm in length.
  • Different populations vary in colour from pale yellow to bright golden.
  • Its fins are dotted with dark spots, giving it its common name.

Sources

17 facts checked with sources