A tiny fish trailing impossibly long black filaments from its fins, which the males raise and flick at each other like ribbons in a slow dance. Delicate in every sense.
Temperament
Common health issues
- Ich (white spot)
- Fin rot
- Skin conditions
- Swim bladder disorder
Care at a glance
- ExerciseModerate
An active swimmer that appreciates open swimming space.
- GroomingAttentive tank care
Sensitive to water quality โ stay on top of testing and maintenance.
- Living spaceNano-tank friendly
Happy in a small, stable, well-filtered tank.
- Owner experienceSome experience helps
A little know-how makes life smoother.
- Commitment3โ5 years
Plan for a long, loving relationship.
Health to watch: Ich (white spot) ยท Fin rot ยท Skin conditions
๐ Care guide
The Threadfin Rainbowfish (Iriatherina werneri) comes from slow, densely vegetated waters in northern Australia and southern New Guinea and reaches only about 3 to 5 cm including the fin extensions. Males carry dramatically elongated dorsal and anal fin rays and spend much of the day in ritualised sparring displays that involve no actual contact. Keep a group of eight or more with several males in a heavily planted tank of 60 litres or more at 24-30C with a pH of 5.5 to 7.5 and soft to medium water, with very gentle flow and a covered top. The critical care point is mouth size: it is extremely small, so this fish needs micro-foods such as crushed flake, powdered fry food, live baby brine, microworms and cyclops, and it will slowly starve on standard flake. It must never be housed with fast, greedy or fin-nipping fish, which will strip its filaments and beat it to every meal. In a quiet species tank with pygmy corydoras or nano rasboras it thrives.
Frequently asked questions
How active is a Threadfin Rainbowfish?
Moderate. An active swimmer that appreciates open swimming space.
How much maintenance does a Threadfin Rainbowfish need?
Attentive tank care. Sensitive to water quality โ stay on top of testing and maintenance.
What tank size does a Threadfin Rainbowfish need?
Nano-tank friendly. Happy in a small, stable, well-filtered tank.
Is a Threadfin Rainbowfish a good fit for first-time owners?
Some experience helps. A little know-how makes life smoother.
How long do Threadfin Rainbowfish live?
3โ5 years. Plan for a long, loving relationship.
What health issues affect the Threadfin Rainbowfish?
Keep an eye out for Ich (white spot), Fin rot, Skin conditions. These are worth raising with your vet, along with any screening they recommend.
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