Threadfin Rainbowfish

The Threadfin Rainbowfish (Iriatherina werneri), also known as Featherfin Rainbowfish, is a rainbowfish species that belongs to the Iriatherina genus.

They are characterized by their beautiful two dorsal fins resembling threads or feathers, which give them their name.

In this article, we will discuss everything there is to know about the Threadfin Rainbowfish, including its appearance, diet, habitat, and more!

Threadfin Rainbowfish Characteristics

Scientific NameThe Iriatherina werneri
OriginNorthern Australia, Indonesia, and Papua New Guinea
Aquarist Experience LevelIntermediate
Size of fish2.0 inches (5.08 cm)
Minimum Tank Size15 gal (57 L)
Aquarium HardinessModerately hardy
Temperature73.0 to 84.0° F (22.8 to 28.9° C)
Diet TypeOmnivore
Lifespan4 years – Can have a life span of about 3 to 5 years when kept in a well-maintained aquarium.
Breeding Temperature78.0° F
Range ph5.5-7.5
Hardness Range5 – 19 dGH
Tank levelTop
Ease of BreedingModerate

Threadfin Rainbowfish Origin & Habitat

The Threadfin Rainbowfish is native to Indonesia, Northern Australia, the Cape York Peninsula, and New Guinea’s islands. 

Also, they live within the Fly River and Merauke River basins.

They inhabit sluggish-flowing streams, ditches, billabongs, freshwater swamps, and freshwater marshes.

All of these locations are crawling with submerged vegetation, as well as floating plants that provide shade for fish and refuge.

Threadfin Rainbowfish History

In 1974, Meinken described the threadfin rainbowfish and gave it the scientific name Iriatherina werneri.

This species was discovered in an irrigation ditch in Western New Guinea (previously known as Irian Jaya).

They have been in the aquarium hobby since 1974, but only males were originally available.

Today, you can find both sexes in the aquarium trade and you can breed them in home aquariums.

Threadfin Rainbowfish Conservation Statue

The conservation status of Threadfin Rainbowfish is Not Extinct. Therefore, no special measures are taken to conserve this species.

What Are the Features of Threadfin Rainbowfish?


The body is brownish and glistening, with silvery marks. 

However, the New Guinea-dwelling individuals are somewhat darker than their Australian counterparts.

Also, both genders are darker on their backs, but it is considerably more evident in males.

In addition, males have thread-like filaments that give the species its common name.

Furthermore, the male is often more colorful, they frequently have a yellow or red first dorsal fin and reddish or crimson caudal fin lobes.


A Threadfin Rainbowfish is a small fish that can only reach up to 2 inches (5.08 cm) in length as adults.


The life expectancy of this species varies from 3 to 4 years depending on how much care they receive.

Threadfin Rainbowfish Availability

Threadfin Rainbowfish (Featherfin Rainbowfish) are available in stores and online. However, they are a bit more expensive than other rainbowfish.

Is Threadfin Rainbowfish Hardy?

Threadfin rainbowfish are moderately hardy fish that are perfect for intermediate aquarists.

However, they are very sensitive to changes in water parameters and can quickly succumb to stress if not properly acclimated.

To minimize stress, it is best to slowly acclimate them to your aquarium since the hardest part for them is recovering from the stress of transportation.

How to Care for Threadfin Rainbowfish?

a.Water Requirements

1. Water Quality

Although threadfin rainbows are not particularly hardy, they are extremely sensitive to water quality.

However, you should not perform major water changes. Instead, you can do small and frequent water changes to help them acclimate to your aquarium slowly.

Therefore, you should do weekly water changes of 25 – 50%, depending on stocking density and how much waste is produced in your aquarium.

2. Water Temperature

These rainbows come from warm waters in Australia and new guinea, so they will do best in aquariums with water temperatures between 77 and 82 degrees Fahrenheit.

If you live in a cooler climate, you may need to use an aquarium heater to maintain these temperatures.

3. pH Level

Threadfin rainbowfish thrive well in slightly acidic water like their wild counterparts.

Therefore, you should maintain the pH value between 5.5 -7.5. It is best to use a pH buffer when setting up your aquarium to avoid any drastic changes.

4. Water Hardness

Threadfin rainbowfish prefer soft water with a hardness of 5 – 19 dGH.

b.Tank Setup

1. Tank Size

Threadfin Rainbowfish are active dwellers in the top levels of the aquarium. 

They are schooling fish, so they should be kept in groups of at least 5.

With that being said, a 15-gallon tank is the minimum tank size you should keep these fish.

2. Tank Lid

These fish are jumpers that leap out of the tank when they’re startled.

Therefore, it is important to have a tank lid that fits snugly on your aquarium.

3. Lighting

Threadfin Rainbowfish come from heavily vegetated areas with little light penetration.

To recreate this environment, you should use low-wattage fluorescent lighting.

4. Decorations

As with many other fish, these rainbowfish will do best in a tank that replicates their natural habitat.

To do this, create a well-planted aquarium with a wide range of plants. This will make them feel secure as well as allow their colors to come out.

If the fish decide to retreat, you can add a few plants that offer dense coverage, including Water Wisteria, Hornwort, and Java Moss.

In terms of the substrate, you can either add sand or gravel or a combination of both.

5. Filtration

Threadfin rainbow fish need a fairly active current to feel comfortable in their tank.

Therefore, you should use a filtration system that can provide this. To achieve this, add an air-powered sponge filter or a canister filter to the fish tank.

Also, the filter will help to keep the water quality high, which is extremely important for these fish.

Threadfin Rainbowfish Compatibility

Threadfin Rainbows are peaceful fish that feel comfortable within the company of different rainbowfish, as long as they have an adequate tank size.

Some of the fish species that get along with threadfin rainbows in the community tank include:

  • Gourami Fish
  • Rainbow Shark
  • Ram Cichlid
  • Loaches
  • Cherry Barb
  • Otocinclus Catfish
  • Guppy Fish

Threadfin Rainbowfish Diet

Threadfin Rainbowfish are omnivorous, so their diet should consist of both meaty and plant-based foods.

In the wild, they consume fruits, algae, plankton, bugs that fall into the water, phytoplankton, and insects.

In captivity, you should give them a balanced diet that consists of:

  • Finely crushed flake foods
  • Frozen or live mosquito larvae
  • Baby brine shrimp nauplii
  • Daphnia
  • Copepods
  • Microworms
  • Artemia
  • Crushed tablet/pellet
  • Grindal

However, keep in mind that you should offer them tiny portions that could fit into their tiny mouths. Large amounts of food might result in severe damage to the fish.

When it comes to the feeding frequency, you should feed them two times to three times each day with an amount they can consume within 5 minutes.

Threadfin Rainbowfish Breeding

The Threadfin Rainbowfish is a simple fish to breed. However, you have to provide them with the right conditions.

Some of the requirements you should do to induce spawning are:

  • Select a pair of mature specimens
  • Introduce them separate breeding tank
  • Maintain slightly acidic and soft water
  • Keep the water temperature at 78° F (26° C)
  • Feed them live foods such as brine shrimp and daphnia
  • Add bushy plants like java moss or include a few spawning mops

When you provide these circumstances, the male threadfin Rainbowfish will court the female around the spawning medium.

Also, the male will extend its first dorsal and anal fins and “flick” them to make himself appear more intimidating.

After spawning, the female will release small eggs that will stick to the plant or spawning mop.

The parents will continue to lay eggs in batches for a few days. 

Therefore, you should move the plant/mop to a separate hatching container to protect the fry.

Since the fry is sensitive, keeping the water quality high is critical. 

You can feed the fry egg yolk or infusoria until they are old enough to accept newly hatched brine shrimp.

Threadfin Rainbowfish Gender Difference

Male and female rainbowfish look exactly the same except for the male’s extravagant fins.

In addition, threadfin males display a wider range of colors than females.

Last Words

The threadfin rainbowfish is a peaceful community fish that does best in a group.

This species is relatively easy to care for, as long as you provide them with the right tank mates and diet.

Also, threadfin rainbowfish are easy to breed in captivity.

We hope this guide was helpful and informative. If you have any questions, feel free to leave a comment below.

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