Threadfin Rainbowfish Care Guide

Threadfin Rainbowfish

Scientific name: Iriatherina werneri
Size: 1.5 – 2 inches
Temperament: Peaceful
Compatibility: Peaceful small fishCare Level: Intermediate
Diet: OmnivorepH: 6 – 8
Temperature: 73 – 86°F
Water Hardness (dGH): 5 – 12°N (89.29 – 214.29ppm)

Natural Habitat: Australia and New Guinea
Swimming Area: Top and mid levels
Minimum Tank Size: 20 gallon
Tank Set-Up: Freshwater with plants and hiding places

Introduction to the Threadfin Rainbowfish

The Threadfin Rainbowfish is a wonderful community fish that is both beautiful and peaceful. The Threadfin Rainbow gets his name from the graceful, elegant flowing fins. Like a peacock, when the male shows off his fins it is an impressive site to see. What makes this fish unique is the male’s flamboyant appearance when he diplays his plumage. The elegant fin display of the Threadfin Rainbowfish is what sets this fish apart from other fish.

Threadfin Rainbowfish

The Beautiful Threadfin Rainbowfish

The beautiful fins casually flow thru the water until two males show off their fins when they compete with other males and to attract the females’ attentions when they are courting females. The males display their fins proudly like flags and their bodies shimmer as they swim.

Similar to other rainbows (family Atherinidae), the Threadfin has two dorsal (top) fins. But the Threadfin or Featherfin Rainbow is one of a few Rainbows where the males have long flowing fins. The dorsal (top) and anal (bottom) fins have huge black “threads”, while the caudal (tail) fins have red or other vibrant colored “threads”.

Rainbowfish in general have large eyes, black or silver band that runs through the middle of their bodies, forked mouth, and two dorsal fins. While the body of the male Threadfin Rainbowfish is mostly silver, the female is much more plain but still possess a lovely honey coloration.

The males have red, orange and blue accents while the females have a slight green hue. A truly dazzling site is to see a school of male and female Threadfin Rainbowfish flutter around together in sync as if they are dancing with each other.

Determining the Gender of Threadfin Rainbowfish

It’s easy to determine gender of this Rainbow. The females are smaller and lack the extravagant fins and are much less colorful.

The body of the Threadfin Rainbowfish is mainly silver or grey with a colored bands running down it’s back and belly, as well as a variety of other colors all over its body.

The Threadfin Rainbowfish can really thrive when the water conditions and enviroment is ideal. In a good environment you will be able to fully appreciate the beauty of the vibrant hues and sparkling scales.

Things to be Aware of when Caring for Threadfin Rainbowfish

This fish can make a fabulous addition to any tank, although there a few quirks that you should be aware of. The main thing to consider is that the fish has a very small mouth and may have issues feeding. This being said, if their special requirements are provided, almost anyone can keep Threadfin Rainbowfish.

What Do Threadfin Rainbowfish Eat

The Threadfin Rainbowfish is an omnivore and feeds on vegetation like algae and diatoms as well as small insects. So small foods like live or frozen mosquito larvae, baby brine shrimp, copepods, daphnia, microworms and grindal are all suitable treats for your Threadfin Rainbowfish. Finely crushed flakes should comprise a decent portion of the fish’s meals.

Because the Threadfin Rainbowfish have tiny mouths, they have some special dietary needs that need to be met to ensure that the fish gets enough food to thrive.

Threadfin Rainbowfish Lifespan & Size

The Threadfin Rainbowfish is fairly small, growing to around 2 inches at maturity but this does not include the Threadfin’s long tail.
They can live up to 5 years with an average livespan of around 3-5 years in a good environment.

Threadfin Rainbowfish in the Aquarium

The Threadfin is a peaceful, schooling fish so I recommend at least 6. I would go with 2 males and 4 females. It’s recommended that there is at least a 2 to 1 ratio of Females to Males. In groups, the Threadfin Rainbowfish feels safe and will show off it’s full beauty when they feel secure in a school.

Since they have long, flowing fins they should only be kept in a tank without fin-nippers.They breed best in tanks of their own species. The male courts the female by posing in front of her repeatedly raising then lowering his beautiful fins.

Threadfin Rainbowfish Tank Mates

Threadfin Rainbowfish thrive in a tank with it’s own species.
The Threadfin can also do well in a tank with other peaceful fish that do not nip on fins. Obviously this is a major concern due to the long, delicate fins of this Rainbowfish that can be easily damaged.

To minimize the risk of fin nipping, keep the Threadfin Rainbowfish with other Threadfins, or other peaceful fish. This stops the other fish from intimidating or bothering them. Some companions that are known to get along successfully are Platys, Mollies, Some Tetras, Guppies, Celestial Pearl Danios, Dwarf Rasboras to name a few.

Cherry Shrimp, Amano Shrimp, Bamboo Shrimp and other large species of shrimp can also be a sound choice. When it comes to creating a community for the Threadfin Rainbowfish, your options should include gentle fish and not agressive fish like Oscars, African Cichlids or other agressive fish.

Natural Habitat

In the wild, the Threadfin Rainbowfish is native to freshwater swamps and thick, planted areas of northern Australia and New Guinea.

The fish inhabits freshwater marshes and slow-moving rivers. They like areas where there is heavy vegetation.
Lilypads appear to be a favorite plant of the Threadfin Rainbowfish, since they are often found swimming around these floating plants.
Schools also are found around driftwood as well.

Threadfin Rainbowfish Care

I would recommend Threadfin Rainbowfish live in a tank of at least 20 gallons for a school of 6 or so.
I would suggest getting a bigger tank if you house more fish. Larger schools require bigger tanks.
It is a very active fish which requires plenty of room to swim around.

The water temperature should generally be from the mid 70s to low to mid 80s F. The Threadfin Rainbowfish prefer soft to moderately hard water, with the pH between 6.0–7.0, but a stable environment is what I would recommend instead of trying to chase water parameters.

The Threadfin Rainbowfish does not require strong current in the tank, since they are used to shallow and slow-moving waters.
They do however need plenty of oxygen, so I would recommend using air stones in your tank.

This peaceful Rainbowfish is a schooling fish that does best in a well planted aquarium. Rainbows appreciate a gravel or sand substrate and may intensify their colors against a dark colored gravel.

Keeping your Threadfin Rainbowfish Happy

There are a certain things to consider to make them happy.
A well planted tank with open swimming spaces at the front is an ideal environment. Some of the fish’s favorite plants include Hornwort, Water Wisteria and Java moss.
The Threadfin Rainbowfish will hide in the plants when it is sleeping or when it needs a hiding place.

The Threadfin Rainbowfish is also known as jumper and has been known to hop out of the tank so I would recommend a lid on your fish tank. You can also provide a gap of space at the top of the tank and you may be witness the sight of the leaping Threadfin Rainbowfish.


The threadfin rainbowfish is not the easiest fish to breed.

Water changes at a slightly cooler temperature may induce them to spawn. Use a spawning mop or clumps of moss as the eggs will need to be removed once they are laid so the parents don’t eat them.
The fry will be very small. Feed with Infusoria until they have grown slightly and then feed with newly hatched brine shrimp.

Sexing is easy by examining fins: males have larger, more flamboyant finnage than females.
Males also have more intense colors.
When reproduction takes place eggs are scattered among the leaves of submerged vegetation, and hatch after 7-10 days.

With the proper care, the Threadfin Rainbowfish can be a great addition to a peaceful, community tank. They also make an excellant centerpiece in a tank by themselves in one big school.

The spectacular dispay of the finnage is a spectacular site to see and the most alluring feature of the Threadfin Rainbowfish

It is important to note that this fish requires special care so it can thrive.
When these special needs are met, I would highly recommend keeping the Threadfin Rainbowfish.