A delicate and exquisitely shaped nano rainbowfish native to New Guinea and Northern Australia. They are famous for the males' long, filamentous fins and butterfly-like display behavior. Due to their incredibly small throats, they require micro-foods. They are shoaling fish that are easily intimidated by boisterous tank mates.
At a Glance
Tank Requirements
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Water Parameters
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Temperament & Compatibility
Available Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Male
Features spectacular long fin filaments and brighter coloration. Males will 'spar' (display) without harming each other. Their fins are fragile and nip-prone.
Differs in 2 traits from base species
Also known as: Display Male
Female
Smaller fins and honey/silver coloration. Essential to keep in the tank to encourage male displaying behavior. Generally smaller than males.
Differs in 2 traits from base species
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🟢Ideal Tank MatesThreadfin Rainbowfish Care Guide Summary
The Threadfin Rainbowfish, scientifically known as Iriatherina werneri, belongs to the Rainbowfish family group. Adults reach a maximum size of approximately 5 cm and have a compressed body shape with a moderate growth rate. Classified as peaceful, this species primarily occupies the surface and mid-level zones of the aquarium and produces a low level of biological waste.
To thrive, the Threadfin Rainbowfish requires a freshwater only aquarium with a minimum volume of 60 litres and a tank length of at least 60 cm. Water temperature should be maintained between 23°C and 29°C, with a pH range of 5.5–7.5 and a general hardness of 1–12 dGH. A low water flow is preferred. An aquarium test kit can help you monitor these values.
The Threadfin Rainbowfish is a rewarding species to keep, provided its core environmental needs are met. This species is available in 2 varieties: Male and Female. Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
Threadfin Rainbowfish Habitat Setup
When setting up an aquarium for the Threadfin Rainbowfish, a low water flow best suits their natural preferences. Because this species occupies the surface and mid-level zones, the aquarium layout should prioritise adequate surface area with floating cover to make them feel secure near the waterline and open swimming space in the centre of the tank for free movement. Useful additions include dense planting to provide cover, break sightlines, and reduce stress and floating plants to diffuse overhead light and create shaded areas. Keepers should note that a tight-fitting lid is essential, as this species is a known jumper.
Threadfin Rainbowfish Compatibility Notes
Classified as peaceful, the Threadfin Rainbowfish is a schooling species that feels most secure in a sizeable group, where natural shoaling behaviour reduces stress and brings out their best colours. When choosing tankmates, shy or slow-feeding tankmates may be outcompeted at feeding time. Selecting tankmates that favour different water layers from the surface and mid-level zones can help reduce competition and territorial overlap.
Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Threadfin Rainbowfish.
20 Gallon High
20 Gallon Long
29 Gallon Standard
30 Gallon Breeder
36 Gallon Bowfront
40 Gallon Breeder
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Frequently Asked Questions About Threadfin Rainbowfish
How big does Threadfin Rainbowfish get?
Threadfin Rainbowfish (Iriatherina werneri) typically reaches a maximum adult size of approximately 5 cm. They have a compressed body shape and a moderate growth rate.
What tank size does Threadfin Rainbowfish need?
A minimum aquarium volume of 60 litres and a tank length of at least 60 cm are recommended for Threadfin Rainbowfish. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Threadfin Rainbowfish need?
Threadfin Rainbowfish thrives in freshwater only conditions with a temperature range of 23–29°C, a pH between 5.5 and 7.5, and a general hardness of 1–12 dGH. A low water flow is preferred.
Is Threadfin Rainbowfish peaceful or aggressive?
Threadfin Rainbowfish is classified as peaceful with an aggression score of 1 out of 10. They are generally well-suited to peaceful community tanks.
How many Threadfin Rainbowfish should be kept together?
Threadfin Rainbowfish is a schooling species and should be kept in groups of at least 6. Larger groups help distribute aggression and encourage natural schooling behaviour.
Does Threadfin Rainbowfish have any special tank requirements?
Yes. Threadfin Rainbowfish benefits from plants - densely covered and plants - floating in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Does Threadfin Rainbowfish need a lid on the tank?
Yes. Threadfin Rainbowfish is a known jumper, and a tight-fitting lid or cover is essential to prevent escape. Even a small gap can be enough for a determined fish to leap out.
Similar Species
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Melanotaenia lacustris
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Forktail Blue-eye
Pseudomugil furcatus
A highly active, nano shoaling fish native to Papua New Guinea. Recognized by their striking blue eyes and energetic swimming patterns. They are peaceful but require open horizontal swimming space and the company of their own kind to thrive. Due to their short lifespan (2-3 years), they mature quickly and display near-constant courtship behavior.
Gertrude's Spotted Blue-eye
Pseudomugil gertrudae
A stunning, highly active nano fish native to Australia and New Guinea. Known for their striking blue eyes and the males' spectacular, heavily spotted fins which they flare during dominance displays. They are peaceful but require being kept in shoals to thrive and exhibit natural behaviors.
Red Rainbowfish
Glossolepis incisus
Native to Lake Sentani in Indonesia, this species is famous for the brilliant salmon-red coloration of mature males. They are large, active schooling fish that develop a distinct high-arched back as they age. Females are vastly different in appearance (olive-gold). They require hard, alkaline water and plenty of swimming space.
Dwarf Neon Rainbowfish (Praecox)
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A brilliant, active schooling fish native to the Mamberamo River basin in West Papua. Known for their iridescent neon-blue bodies, they are an energetic and peaceful addition to community tanks. Because of their high activity levels, they require ample open swimming space alongside planted areas. They are fast eaters and may outcompete shy tank mates for food.
Celebes Rainbowfish
Marosatherina ladigesi
An active, schooling fish native to the karst (limestone) streams of Sulawesi, Indonesia. Known for their striking neon blue lateral stripes and yellowish fins. They strictly require hard, alkaline water to thrive and are highly sensitive to soft, acidic conditions. A peaceful species that requires plenty of open swimming space.