Threadfin Rainbowfish (Iriatherina werneri): Ultimate Care Guide


Do you love keeping tropical fish as a hobby? If so, you’ll want to learn all about the Threadfin Rainbowfish.

With their bright colors and lively personalities, they are sure to bring a touch of happiness to your home. Our guide will provide everything you need to know to keep your Threadfin Rainbowfish healthy and happy.

 So read on for all the details!

The Threadfin Rainbowfish is a tropical freshwater fish that is a colorful and uniquely shaped fish that can be kept in freshwater aquariums by hobbyists of all skill levels.

Threadfin Rainbowfish is a small member of the family Melanotaenidae – perhaps one of the smaller at only two inches. It comes from an area covering parts of New Guinea and northern Australia.

Hopefully, the following article will be a good reference guide for those interested in this magnificent and undemanding freshwater fish species.

It’s no secret among aquarists that the Threadfin Rainbowfish is one of the easier species to care for, and the research created in this ultimate guide will give you everything you need to know about keeping this gem healthy in your tank.

Threadfin Rainbowfish
Threadfin Rainbowfish (Iriatherina werneri)

Threadfin Rainbowfish Care

Threadfin Rainbowfish are hardy fish that can be kept in various aquarium conditions. They are tolerant to a range of water temperatures and pH levels, making them an ideal choice for both novice and experienced aquarists. In addition, Threadfin Rainbowfish are peaceful fish that do not typically harass other inhabitants of the aquarium.

Threadfin Rainbowfish Temperature & Water pH

The ideal temperature range for keeping Threadfin Rainbowfish is 73-84F. Rainbowfish will do best in slightly acidic water with a PH of 5.5-7.5. 

The minimum recommended water temperature for this species is 73°F or 22°C. Threadfins are very cold sensitive, so the water temperature should not drop below 68°F (20°C) at any time; if necessary, heaters should be used to maintain warmer temperatures.

Threadfins prefer water hardness in the range of 5 – 19 dGH

Threadfin Rainbowfish Size

The average size of a Threadfin Rainbowfish is about 2 inches long. Males can get a bit larger at 2.5 inches long. The fins keep growing as the fish ages which gives it an almost royal look.

Threadfin Rainbowfish Origin

The Threadfin rainbowfish originates from Australia and Papua New Guinea. They are primarily found in the warmer waters of creeks and rivers around the Northern parts of Queensland.

The Threadfin Rainbowfish was scientifically named by Meinken and given its current name in 1974.

Meinken found the Threadfin Rainbowfish in an irrigation ditch in the middle of nowhere in papa New Guinea. Could you ever imagine a drain would contain such a beautiful fish?

Threadfin Rainbowfish Tank Size

20-gallon tank size is the recommended minimum for keeping Threadfin Rainbowfish. This will give them plenty of room to swim and explore.

Threadfins are social fish that prefer living in groups, so if you have a small tank, it’s important to note that they can become stressed if they are the only fish in the tank. They do not compete well with fin nippers because their fins are susceptible to damage.

Threadfin Rainbowfish Food & Diet

Threadfin Rainbowfish are omnivorous and eat a variety of foods. They will consume both plant and animal material. A good diet for them includes a variety of live and frozen foods and dried food.

Their diet can also include various types of algae. The best way to introduce new foods to the Threadfin Rainbowfish is by feeding vegetable-based dried food items with natural insect material.

Threadfin Rainbowfish Lifespan

Threadfin Rainbowfish in the wild typically live around 2-3 years, though this is usually shorter in the wild because of predation and other dangers. In captivity, it is common to live up to 5 years.

The Threadfin Rainbowfish is generally classified as a hardy fish because it can survive under crowded conditions.

They can be kept in a community tank as long as they are not with large or aggressive fish because the Threadfin Rainbowfish is not such an active or fast swimmer.

Keep them under the right conditions and they can live over five years, stress will shorten any fish’s life.

Threadfin Rainbowfish Fish Tank Setup

The Threadfin Rainbowfish is a shoaling, stream-dwelling fish. It originates from well-oxygenated, slow-moving rivers and creeks of the Northern Territory and papa new guinea.

These conditions allow for little light penetration, meaning that the waters are stained with tannins, turning them a tea color.

The ideal conditions for the Threadfin Rainbowfish are as such:

The Threadfin Rainbowfish is a hardy fish that requires 20 gallons of water to thrive. They like schools, and it’s best if you have ten or more individuals in your tank so they can show off their beautiful colors properly!

Experts recommend having three females per male. The tank must mimic their natural habitat to keep these fish healthy and happy.

The substrate should be fine gravel or sand with various plants for them, which will help them feel safe from danger while bringing out their colors!

Threadfin Rainbowfish Breeding

Threadfin Rainbowfish is a hardy fish with no parental care. If you provide it the opportunity, it will eat its eggs and fry!

The best way to breed is to set up separate a tank for fish breeding, it can be complicated, but this process will help you get started. 

The first step is to separate one male and two or three females and put them in a separate tank with java moss as spawning media.

It’s important that these surfaces are not only clean but also soft, so your lady friends have somewhere comfortable enough to lay their eggs!

You should check daily, and If you find any eggs, remove them to a separate hatching container. 

This will allow more chance of fry survival!

Threadfin Rainbowfish Male or Female

The Threadfin Rainbowfish has a tan color with five black bands that run horizontally across its body. There are two slightly smaller black bands on the dorsal fin and one large black band near the anal fin. The last band is underneath the fish’s anal fins but is not always fully connected. 

The fins on its back end are a blue/green color, and the belly is silver in color.

Males have more elongated pointed dorsal and ventral fins than females do.

Threadfin Rainbowfish Diseases 

Threadfin Rainbowfish are prone to various diseases, including skin fluke, ichthyobodo infection, parasitic infestations, bacterial infections, and bacterial disease.

Goiters are a common issue in fish that dietary deficiencies can cause. Iodine is usually lacking from the food.

When owning one of these guys, the key thing you need is to make sure they have enough iodine. Feed them foods specially formulated with iodine.

Threadfin Rainbowfish Tank Mates

Threadfin Rainbowfish will not bother any tank mates, including invertebrates and smaller fish species. Males may fight over territory if housed together in a small tank.

Threadfin rainbowfish are peaceful creatures that can suffer on their own. Due to being tiny and cautious, they’re at risk for malnutrition because they can’t compete for food!

Threadfin rainbows are among the more peaceful species in this category, so it’s not surprising that they can be kept with other small tropical community fish.

Other compatible fish types are Rainbow Shark, Loaches, Ram Cichlid, Cherry Barb, Gourami Fish, Guppy Fish, Otocinclus Catfish, etc.

Are Threadfin Rainbowfish Schooling fish?

Threadfin Rainbowfish are schooling fish by nature, which means they like to swim in groups. These fish enjoy being in groups of six or more. This means if you only have one or two Threadfin Rainbowfish, they can become stressed and sick.

However, males are very protective of their group members when in a group. They are also well known for protecting other fish in the community tank from being bullied by other fish. 

They are very peaceful fish that will not harm other tank mates unless attacked. Threadfin Rainbowfish are popular aquarium fish because of their long, colorful dorsal fin.

Why should you get a Threadfin Rainbowfish?

This beautiful little fish is an excellent option for an aquarium, especially if you’re looking to add some color. The Threadfin Rainbowfish is a resilient fish that can thrive in many different aquarium conditions. 

They are easy to keep and make great beginner tropical fish for anyone looking to start their first freshwater tank.

The Threadfin Rainbowfish is a perfect little fish for your aquarium. They can be very social and fun to watch, but they’re also small enough that you won’t have to worry about them taking over the tank!

Threadfins enjoy swimming in calm waters with dense plant life and places where they can dart in and out of holes. They also want open spaces where they can stay near the top of the tank without being confined. 

If you’ve been thinking about adding some new life into your home but don’t know where to start, the Threadfin Rainbowfish could be just what you’re looking for!

Fish Laboratory

With decades of collective fishkeeping experience, we are happy to share the fish care tips that we've picked up along the way. Our goal at Fish Laboratory is to keep publishing accurate content to help fishkeepers keep their fish and aquarium healthy.

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