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Maximum size : 3 - 5 cm

Threadfin Rainbowfish - Iriatherina werneri : Complete Fish Profile & Care Guide

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The Threadfin Rainbowfish, (Iriatherina werneri) is a stunningly elegant and peaceful species, making it a highly sought-after addition to any aquarium. However, caution is needed when selecting tankmates, as these fish are easily outcompeted for food and their fins can get nipped by aggressive species. To showcase their full potential, it is recommended to keep these fish in small groups of at least six, with a male-to-female ratio of 1:2. The males display stunning feather-like patterns to outdo their rivals while vying for female attention, resulting in a breathtaking display of colors. The aquarium should be at least 2ft long and feature plenty of darkly furnished hiding spots with rooted and floating plants. Regular partial water changes are essential, and gentle water circulation should be provided. These fish possess silver bodies and a vast array of colors that sparkle with vibrant tints and shimmering scales, depending on their environment and diet. The long, elegant fins make them truly captivating to observe in action. The Threadfin Rainbowfish is an excellent choice for those looking to add some unique flair to their aquarium.

Threadfin Rainbowfish Photos

Sexual Dimorphism

Distinguishing between male and female Threadfin Rainbowfish is a straightforward task with this species. Male Threadfin Rainbowfish exhibit a silver hue, coupled with larger and more ornate fins. They also display more vibrant and intense colors. In contrast, female Threadfin Rainbowfish display a golden tone and lack the extravagant fins that are characteristic of males.

Quick Facts

Scientific NameIriatherina werneri
Year Described1974
Other NamesFeatherfin Rainbow
OriginsPapua New Guinea Australia
Max Size3 - 5 cm
Aquarium LevelTop
Best kept asGroups 6+
Lifespan3 - 5 years

Water Parameters

Water TypeFreshwater
PH5 - 8
GH3 - 10
KH7 - 10
TDS20 - 220
71 - 86
21.7 - 30

Natural Habitat

The Threadfin Rainbowfish 's native habitat is in New Guinea and Northern Australia! These stunning fish can be found in slow-moving streams, lagoons, freshwater marshes and freshwater swamps, containing clear water and abundant macrophytes. They can also be found in the lakes Kala and Bosset. In their natural environment, Threadfin Rainbowfish inhabit thickly vegetated areas associated with driftwood and Lilly pads, providing them with sun-filtered shade and shelter that they require to thrive. The lush vegetation and tranquil waters of their habitat offer a serene and enchanting environment where these remarkable fish can feed, breed, and play. Recreating the perfect environment for Threadfin Rainbowfish in your home aquarium requires a bit of effort, but the rewards are well worth it. So why not take a plunge into the fascinating world of New Guinea and Northern Australia 's aquatic life and discover the wonders of Threadfin Rainbowfish for yourself?


As egg-scatterers, Threadfin Rainbowfish do not offer any parental care to their offspring and will readily consume their own eggs and fry if given the opportunity. There are two methods for breeding Threadfin Rainbowfish. The first entails placing a single male and two to three females into a smaller aquarium, complete with a spawning medium such as java moss or a spawning mop, and an air-powered sponge filter. These tanks should be monitored daily, and any eggs discovered should be transferred to a separate hatching container to improve the chances of fry survival. An alternative approach to breeding Threadfin Rainbowfish is to maintain a colony of adult fish in a spacious, well-decorated aquarium. In such a setup, some of the fry may survive if there is sufficient vegetation. For the best chance of fry development, consider adding floating plants with trailing roots or aquatic moss attached to decor high in the water column. This is because the fry spend their early life stages close to the water 's surface, where they can easily access these vital resources. During the spawning process, the male will exhibit a courtship display to the female, usually under the cover of floating plants. Once the female is receptive, she will choose a suitable spawning site, often fine-leaved vegetation or the roots of floating plants. Once settled, the female will signal to the male by remaining still in the chosen spot. Together, the male and female will release milt and eggs into the medium. The female deposits multiple eggs daily for several days until all of their eggs have been laid. In the presence of multiple females in the same tank, the male may mate with each of them on the same day. Ensuring optimal tank conditions is crucial to increase the chances of Threadfin Rainbowfish fry survival. Rearing the fry can be a challenging task, requiring close attention to water quality, diet, and suitable tank mates. With the appropriate care and maintenance, however, watching these delicate and stunning fish grow and thrive can be a rewarding experience for any aquarist.

Diet & feeding

A well-rounded diet for Threadfin Rainbowfish should ideally include a significant portion of live foods such as Daphnia, Artemia, Moina, micro worms, and copepods. However, they can also accept small crushed floating dried foods such as flakes and granules. It is important to note that these fish have small mouths, so it is necessary to ensure that the food provided is of a suitable size.

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