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Encyclopedia / Rainbowfish / Threadfin rainbowfish
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Variations

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Threadfin rainbowfish

Iriatherina werneri · Threadfin

Peaceful; avoid fin-nippers.

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4 cmBody length, without tail ✓
24–29 °CTemperature ✓
6–7.5pH ✓
54 LSmallest tank ✓
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Tank mates
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Not recommended
  • Black skirt tetra nips fins, and Threadfin rainbowfish has long fins.
Not recommended
  • Serpae tetra nips fins, and Threadfin rainbowfish has long fins.
Not recommended
  • Tiger barb nips fins, and Threadfin rainbowfish has long fins.
With conditions
  • Only a narrow temperature range suits both: 24–25 °C.
With conditions
  • Only a narrow temperature range suits both: 24–25 °C.
Compatible
Compatible
Compatible
Compatible
Compatible

295 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 ✓1–12 dGH
Group size ✓6 or more
Temperament ✓Peaceful
Swims at ?Top
Care level ✓Moderate
Diet Omnivore
Lifespan ✓2–3 years
Size in shops 2–3 cm
Growth Medium

Behavior

Peaceful; avoid fin-nippers.

Food

Micro foods.

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Male or female

Mature males have a fan-shaped first dorsal fin and very long thread-like filaments on the second dorsal, anal and pelvic fins, and are larger and more colourful; females are plain with short fins.

Health

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

Breeding

Egg-scatterer · Moderate

Lays a few eggs each day over several days on fine-leaved plants, aquatic moss or nylon mops.

Pairing

Group of 8+.

Setup

A planted tank with fine mops.

What starts it

Frequent feeding, good conditions.

Eggs

A small number of eggs each day for several days; eggs hatch in 7-10 days depending on temperature.

Raising the fry

Fine infusoria, microworms.

Common mistakes
  • Tank too turbulent
  • Large tank mates
  • Poor food
Full breeding guide, day-by-day plan and simulator →

Where it lives in the wild

RegionSouthern New Guinea and northern Australia (Cape York)
Rivers and lakesCoastal rivers and swamps of southern New Guinea and Cape York
HabitatWeedy swamps and slow streams
Native rangeAbout 700 km across
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The story of the threadfin rainbowfish

Males display spectacular thread-like fins. Two German aquarists collected it in a New Guinea rice paddy in 1973, and Herman Meinken described it in 1974, naming it after collector Arthur Werner. It was later also found in Australia's Cape York Peninsula.

German aquarist and ichthyologist Hermann Meinken described the threadfin rainbowfish in 1974. Males grow long, thread-like extensions on their fins, which they spread in courtship displays. It is a small, delicate fish best kept with calm tankmates.

First described by Hermann Meinken in 1974.

  • Males have long, thread-like fins.
  • It is only about 5 cm long.
  • It needs calm tankmates.

Sources

17 facts checked with sources