Threadfin Rainbow

Threadfin Rainbow
Latin name:
(Iriatherina werneri)

Care Level





Blue, Grey



Preferred Conditions

72-77° F, KH 7-10, pH 6.0-7.2

Avg. Max Size


Minimum Tank Size

10 gallons


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In the vast world of aquarium fish, the Threadfin Rainbow stands out as a true gem. With its vibrant colors, active behavior, and adaptability, this fish is a popular choice among hobbyists of all levels. So, what makes the Threadfin Rainbow so special? Let’s dive in and explore this fascinating creature.

Threadfin Rainbow: A Profile

The Threadfin Rainbow, scientifically known as Iriatherina werneri, is a species of rainbowfish native to the Fly River system in Papua New Guinea. These fish are characterized by their elongated, torpedo-shaped bodies, which are adorned with a stunning array of colors. The males typically display a brilliant blue coloration with red and yellow accents, while the females are generally more subdued, exhibiting a silvery-green hue.

Threadfin Rainbows are known for their active and lively behavior. They are schooling fish, meaning they thrive in groups, and can often be seen swimming in synchronized formations throughout the aquarium. Their playful nature and vibrant colors make them a joy to watch.

Ideal Tank Setup for Threadfin Rainbows

To ensure the well-being and happiness of your Threadfin Rainbows, it’s essential to provide them with an appropriate tank setup. Here are some key considerations:

Tank Size:

Threadfin Rainbows are relatively small fish, but they require a spacious tank to thrive. A minimum tank size of 20 gallons is recommended for a small group of these fish. However, a larger tank is always better, as it provides more swimming space and reduces the risk of overcrowding.

Water Parameters:

Threadfin Rainbows prefer slightly acidic to neutral water conditions. The ideal pH range is between 6.5 and 7.5. The water should also be soft to moderately hard, with a hardness range of 5 to 15 dGH. To maintain optimal water quality, regular water changes are essential.

Filtration and Water Flow:

Threadfin Rainbows are active swimmers and appreciate a moderate to strong water flow. A powerful filter system is necessary to maintain good water quality and provide adequate oxygenation. A combination of a sponge filter and a power filter is often recommended.

Substrate and Decorations:

Threadfin Rainbows prefer a sandy or fine gravel substrate. They also appreciate the presence of live plants, which provide hiding spots and help maintain water quality. When selecting plants, choose species that can tolerate the slightly acidic water conditions preferred by these fish.

Diet and Feeding Habits of Threadfin Rainbows

Threadfin Rainbows are omnivorous and have a varied diet. They readily accept a wide range of foods, including live, frozen, and freeze-dried foods. A staple diet of high-quality flake food or pellets is recommended, supplemented with live or frozen foods such as brine shrimp, daphnia, and bloodworms. To ensure a balanced diet, offer a variety of foods and avoid overfeeding.

Breeding Threadfin Rainbows

Breeding Threadfin Rainbows in captivity is possible with a little planning and care. Here are some key steps to follow:

Selecting a Breeding Pair:

Choose a healthy and sexually mature pair of Threadfin Rainbows. The males are typically more colorful and have longer fins than the females. Introduce the pair to a separate breeding tank that is densely planted and has soft, acidic water.

Spawning Process:

Condition the breeding pair with a high-quality diet and maintain stable water parameters. When the female is ready to spawn, she will lay her eggs among the plants. The male will then fertilize the eggs.

Raising the Fry:

Once the eggs hatch, the fry will need to be fed infusoria or newly hatched brine shrimp. As they grow, you can gradually introduce larger foods, such as daphnia and finely crushed flake food. Keep the fry in a separate tank until they are large enough to be introduced to the main aquarium.

FAQs About Threadfin Rainbows

Here are some common questions that affiliate marketers may have about Threadfin Rainbows:

Q: Are Threadfin Rainbows easy to care for?

A: Yes, Threadfin Rainbows are generally considered easy to care for, making them suitable for both beginner and experienced aquarists.

Q: What are some common challenges in keeping Threadfin Rainbows?

A: Maintaining stable water parameters, providing a suitable diet, and preventing overcrowding are some common challenges that aquarists may face when keeping Threadfin Rainbows.

Q: What makes Threadfin Rainbows a good choice for aquariums?

A: Threadfin Rainbows are active, colorful, and relatively easy to care for, making them a popular choice for aquariums. Their hardiness and adaptability also make them suitable for a wide range of aquarium setups.


The Threadfin Rainbow is a captivating fish that brings beauty, activity, and hardiness to any aquarium. With its vibrant colors, playful behavior, and adaptability, this fish is a joy to keep and observe. Whether you’re a seasoned aquarist or just starting out, the Threadfin Rainbow is sure to impress and delight.