Why is my Threadfin Rainbowfish spitting out its food?

This is almost certainly because the food is too large. Threadfin Rainbowfish have incredibly narrow throats and will spit out anything they cannot swallow. You must crush flake food into a fine powder or feed micro-foods like Daphnia or baby brine shrimp.

Do I need to keep a specific ratio of males to females?

A ratio of one male to two females is ideal, as it reduces harassment and encourages natural breeding behaviours. However, male-only groups can also be kept without issue, and they will constantly display their fins to one another.

Will they eat my cherry shrimp?

No. Due to their tiny mouths and throats, Threadfin Rainbowfish are one of the most shrimp-safe fish available in the hobby. They cannot eat adult or even most juvenile shrimp, though newly hatched shrimplets might occasionally be picked off if caught in open water.

Why are my Threadfins hiding at the back of the tank?

This usually indicates stress. Ensure the aquarium has plenty of dense planting and floating plants to make them feel secure. Also check that your water parameters are stable and that their tankmates are not overly aggressive or active.

Can I keep Threadfin Rainbowfish with Betta fish?

It is generally not recommended. The spectacular fins of the male Threadfin can trigger a Betta's aggressive response, leading to the Threadfins being chased or having their fins nipped.

FreshwaterTropicalIntermediate

Threadfin Rainbowfish

Iriatherina werneri

The Threadfin Rainbowfish is a captivating, delicate shoaling fish beloved for the spectacular, feather-like fin extensions of the males.

List this species for sale Find Threadfin Rainbowfish near me

Ideal Conditions

Temperature: 23 – 30 °C
pH range: 5.5 – 7.5
Hardness: 1 – 10 dGH
Adult size: 3.5 – 5 cm
60L for a small shoal: 60 litres+
Lifespan: 3 – 5 years
Diet: Omnivore/Micro-predator
Water flow: Gentle
Preferred setup: Densely planted with open swimming space in the centre and floating plants to diffuse light

About the Threadfin Rainbowfish

Boasting an elegant silhouette, the Threadfin Rainbowfish (Iriatherina werneri) is a stunning addition to the peaceful planted aquarium. While females are relatively plain, males develop dramatic, elongated fin rays which they flick open like fans to show off to rivals and mates. Despite their delicate appearance, they are active swimmers that bring constant but gentle movement to the middle and upper levels of the tank.

Find Threadfin Rainbowfish

Search current listings in your chosen area. If none are available, save an alert and we’ll let you know when a match is listed.

Find locally Check compatibility Add to a Setup

Availability alerts only use public sale listings. Adding this species to a Setup updates your private records.

Is it right for your tank?

Check Threadfin Rainbowfish against a habitat you already keep. We compare water type, temperature, pH, adult size, group needs and everything living there.

Where Threadfin Rainbowfish comes from

Native range

Fly River basin, Cape York Peninsula, Northern Territory

Countries / regions

Australia, Papua New Guinea

Habitat

Slow-moving, heavily vegetated billabongs, swamps, and clear or tannin-stained streams.

Populations exist in both southern New Guinea and northern Australia, sharing similar tropical swamp habitats.

Similar species

Forktail Blue-eye
Pseudomugil furcatus
Spotted Blue-eye
Pseudomugil gertrudae
Pacific Blue-eye
Pseudomugil signifer

We’re adding more full species guides as the catalogue grows.

Compatible tank mates

Reviewed guidance based on this species' recorded traits.

View all compatibility

Pygmy Corydoras
Corydoras pygmaeus
Peaceful, small bottom-dwellers that will not compete for mid-water food or harass the Threadfins.
Great
Ember Tetra
Hyphessobrycon amandae
Similarly sized, peaceful schooling fish that share the same preference for planted tanks and gentle flow.
Great
Cherry Shrimp
Neocaridina davidi
The Threadfin Rainbowfish's extremely small mouth means adult and juvenile shrimp are completely safe.
Great
Zebra Danio
Danio rerio
Too active and boisterous; they will outcompete the timid Threadfins at feeding time.
Compatible with caution
Tiger Barb
Puntigrus tetrazona
Notorious fin-nippers that will easily destroy the delicate, trailing fins of the male Threadfin.
Not recommended

Current marketplace listings

Checking the marketplace…

See all Threadfin Rainbowfish listings

Public Wanted requests

No open requests for Threadfin Rainbowfish in this market yet.

Looking for Threadfin Rainbowfish?

Search current listings near you, or post a wanted request so local sellers know what you’re looking for.

Search Threadfin Rainbowfish listings Post a wanted request