Max Size: 3 - 5cm

Threadfin Rainbowfish (Iriatherina werneri)

The Threadfin Rainbowfish is a small fish that holds excellent appeal. They are very peaceful but are not recommended for a community aquarium as they are easily outcompeted for food, and their fins may get nipped by other fish species.

They are best kept with their species or amongst other fish comparable in disposition and size.

The Threadfin Rainbowfish sport long, elegant fins, and the male displays a feather-like pattern, which is especially impressive.

These fish are silver in colour and a significant number of other colours all over their body, which is dependent on the environment, diet, etc.

When provided with perfect conditions, the Threadfin Rainbowfish can sparkle, featuring vibrant tints and shimmering scales. This fish can make a compelling addition to any tank.


Threadfin Rainbowfish
Threadfin Rainbowfish
Threadfin Rainbowfish
Threadfin Rainbowfish
Threadfin Rainbowfish Sparring
Threadfin Rainbowfish
Quick Facts
Scientific NameIriatherina werneri
Other NamesFeatherfin Rainbow
OriginsAustralia, Papua New Guinea
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℃


In the home aquarium, the Threadfin Rainbowfish will readily accept most good quality dried foods such as granules, flakes and sinking pellets. These modern food products have been developed to provide all adequate nutrition to maintain your fish's health and dietary requirements.

Providing additional foodstuffs such as live, frozen, and freeze-dried meals such as bloodworm, daphnia, and tubifex once or twice a week will provide additional benefits to your fish's health and well-being but is not a must for this fish.

It should be noted that bloodworms should only be given as an occasional treat and should not be used as the staple diet as they are difficult for fish to digest and can potentially cause blockages.

This fish is an omnivore in the wild, meaning it will consume some vegetable matter. Although most modern fish foods take this into account and include them in their products, you can still supplement your fish's diet with blanched vegetables such as spinach, broccoli, and zucchini. Ensure you do not overfeed your fish and remove any leftovers the following day.

Sexual Dimorphism

Differentiating between males and females is easy with this species.

The males are silver in colour, have more ornate, larger fins than females, and display more intense colours, whereas the females are more golden toned and lack the fabulous fins.


Breeding the Threadfin Rainbowfish is straightforward once these fish are happily established and settled into your aquarium. You will need a mature pair or group of males and females, along with a spawning mop, preferably floating at the top of the aquarium downwards to the substrate.

Despite spawning year-round, Rainbowfish lay many eggs at the beginning of the rainy season. In addition, temperature increases, and live and frozen foods often encourage spawning.

Check your spawning mops daily for any eggs that have been deposited and either remove the eggs from the mop or, better still, remove the entire mop to avoid contamination of the Rainbowfish eggs.

Tip: Have several spawning mops at hand so you can place a fresh spawning mop into the aquarium while you wait for the eggs to hatch on the other mop/s.

Place the spawning mop with eggs still attached into a separate small cycled aquarium with a sponge filter for flow, and add a few drops of Methylene Blue (Methylene Blue helps prevent fungal infections of eggs).

Your rainbowfish Eggs will hatch within 7 to 18 days, depending on the species and the temperature. We recommend 27°C = 80.6°F for the fastest development of fry.

Once the Rainbowfish fry hatch, they absorb their yolk sacs quickly and become free swimming, moving towards the water's surface. Once the fry reaches the water's surface, you can start feeding. We recommend feeding on Micorworm (the most straightforward live food to culture) and decapsulated brine shrimp egg powder several times a day while being careful not to overfeed and pollute the water column.

After a week or two, you can start to add newly hatched brine shrimp, but this isn't necessary to achieve a high success rate in our experience.

Rainbowfish fry grows slowly, so you should expect to wait several months before the fry is large enough to be added to the adult colony.

Other Rainbowfish of interest

Banded Rainbowfish(Melanotaenia trifasciata)
Boesemans Rainbowfish(Melanotaenia Boesemani)
Celebes Rainbowfish(Marosatherina ladigesi)
Dwarf Neon Rainbowfish(Melanotaenia praecox)
Forktail Blue Eye Rainbowfish(Pseudomugil furcatus)
Honey Blue Eye Rainbowfish(Pseudomugil Mellis)
View all Rainbowfish
Date Added: 28/08/2020 - Updated: 12/08/2022 13:24:06