Threadfin Rainbowfish – Diet, Habitat, Tank Mates & Full Details!

As part of the Melanotaenidae family, Threadfin Rainbowfish distinguish themselves as one of the smallest yet vibrant members, reaching a maximum size of two inches.

Originally found in the water bodies of New Guinea and northern Australia, these fish exhibit a unique blend of hues and an ebullient temperament that fills your aquarium with a sense of liveliness.

Undoubtedly, the addition of Threadfin Rainbowfish is a fantastic choice for aquarium enthusiasts of all proficiency levels.

Whether you are a beginner aquarist looking for a low-maintenance species or an expert seeking a new vibrant species, the Threadfin Rainbowfish caters to all your needs.

Being passionate about maintaining a tropical aquarium in your abode brings joy, serenity, and an intimate connection to nature’s wondrous diversity.

If you are such an enthusiast, then expanding your knowledge about the captivating Threadfin Rainbowfish (Iriatherina werneri) is essential.

In this comprehensive guide, we delve into the world of this tropical freshwater species, revealing insights about their unique characteristics, optimal living conditions, and ideal care routines to ensure your Threadfin Rainbowfish live a vibrant and healthy life.

Quick Stats About Threadfin Rainbowfish

Scientific Name Iriatherina werneri
Common Names Threadfin rainbowfish, Featherfin rainbowfish
Family Melanotaeniidae
Origin New Guinea, Northern Australia
Diet Omnivore
Care Level Moderate
Activity Active
Lifespan 3 to 5 years
Temperament Peaceful
Tank Level Middle
Minimum Tank Size 20 Gallons
Temperature Range 72 to 82° F
Water Hardness 7 to 10 KH
pH Range 6.0 – 7.2
Filtration/Water Flow Slow
Water Type Freshwater
Breeding Egg Scatterer
Difficulty to Breed Moderate
Compatibility Community tanks

Threadfin Rainbowfish Appearance

With a keen eye for beauty and brilliance, it’s hard to overlook the enchanting appearance of Threadfin Rainbowfish.

Their elongated bodies, reminiscent of a delicate thread, come alive in a stunning palette of colors that can transform your aquarium into a vibrant underwater paradise.

Threadfin Rainbowfish showcase a tan-colored body, interspersed with five distinct black bands that horizontally stripe their bodies.

Adding to their charm are two slightly smaller bands on the dorsal fin and a bold black band near the anal fin. They sport a majestic pair of fins on the rear end that gleam in blue and green shades, setting a stark contrast against their silver bellies.

The gender differences in Threadfin Rainbowfish can be seen in their fins.

Male Threadfin Rainbowfish exhibit longer and more pointed dorsal and ventral fins compared to their female counterparts, providing an easy way to differentiate between the two sexes.

Natural Habitat of Threadfin Rainbowfish

To provide optimal care for your Threadfin Rainbowfish, understanding their natural habitat is key.

These tropical freshwater fish originate from oxygen-rich, slow-moving rivers and creeks in Northern Territory and Papua New Guinea.

In these water bodies, the limited light penetration results in a tea-like hue, as the water is imbued with tannins.

Simulating this environment in your home aquarium, with the addition of aquatic plants, not only caters to the comfort of your Threadfin Rainbowfish but also enhances their vibrant colors.

Threadfin Rainbowfish Origin and Distribution

Threadfin Rainbowfish owe their scientific name, Iriatherina werneri, to Meinken who identified this species in 1974.

The surprising discovery of these radiant fish took place in an irrigation ditch, nestled amidst the remote corners of Papua New Guinea.

Unraveling the beauty of Threadfin Rainbowfish from such an unexpected location underscores the diversity and wonders of nature.

In the wild, Threadfin Rainbowfish primarily inhabit the warm waters of rivers and creeks in northern Australia and Papua New Guinea. They are particularly common in Queensland’s Northern regions.

Threadfin Rainbowfish Growth, Size, & Lifespan

Threadfin Rainbowfish, though petite in size, compensate with their flamboyant presence. Reaching a maximum length of 2.5 inches, with males slightly larger than females, their size suits them for a variety of aquarium settings.

It’s fascinating to note that as they age, their fins continue to grow, bestowing upon them an almost regal appearance.

In terms of lifespan, Threadfin Rainbowfish lead relatively short lives in the wild, typically surviving for about 2 to 3 years due to predation and other environmental hazards.

However, in a well-managed captive environment free of such risks, they can live up to 5 years, adding long-term vibrancy to your aquarium.

Taking care of Threadfin Rainbowfish in the right conditions not only extends their lifespan but also contributes to their overall health and well-being.

Ensuring a stress-free environment is vital, as high-stress levels can potentially shorten any fish’s life. So, as an aquarist, prioritizing the well-being of your Threadfin Rainbowfish can pave the way for a gratifying and rewarding experience.

Threadfin Rainbowfish Behavior and Temperament

Threadfin Rainbowfish are the epitome of tranquil aquatic inhabitants. Their peaceful demeanor pairs well with their captivating appearance, making them a popular choice for aquarium enthusiasts.

These fish are renowned for their social nature, thriving in groups.

In fact, the larger the group, the happier these colorful fish seem to be. Their gregarious nature often sees them engaging in playful chases and dances, particularly during mating seasons.

Threadfin Rainbowfish Tank Setup

Now that we’ve explored the beauty and demeanor of Threadfin Rainbowfish, let’s delve into the intricacies of setting up their home – the aquarium.

Tank Size

The Threadfin Rainbowfish may be small, but they appreciate room to roam. A minimum of 10 gallons is recommended for a group of these fish.

Larger tanks, especially those that are elongated, allow them to display their natural schooling behavior to the fullest.


As these fish hail from water bodies with a dark, tea-like hue, they’re accustomed to darker substrates. Utilizing fine dark sand or gravel mirrors their natural environment, enhancing their comfort and color vibrancy.

Decorations and Hiding Spots

Threadfin Rainbowfish relish the comfort of shaded areas and hiding spots. Incorporate aquatic plants, driftwood, and rocks to recreate a natural river environment.

Such arrangements provide them with a sense of security, aiding in their overall well-being.

Water Parameters

Mimicking their native habitat conditions is crucial. Maintain a temperature range between 22-28°C, pH levels from 5.5 to 7.5, and a water hardness of 5-12 dGH.

Filtration and Aeration

A slow-moving current, mimicking their native rivers and creeks, is ideal for Threadfin Rainbowfish. A gentle filter that doesn’t create strong currents is recommended.

A well-oxygenated environment also enhances their health and vitality.


Moderate lighting conditions are suitable for Threadfin Rainbowfish. This level of light aids in the healthy growth of aquatic plants, which in turn provides necessary shade for these fish.

Tank Mates

Being peaceful in nature, Threadfin Rainbowfish do well with other non-aggressive species. Ideal tank mates include similarly sized tetras, guppies, and other rainbowfish species.


Threadfin Rainbowfish are omnivores with a diet that includes a mix of commercial flakes or pellets and live or frozen foods like brine shrimp or daphnia.

A balanced diet aids in maintaining their vibrant coloration and overall health.

Setting up an environment that closely resembles their natural habitat, taking into account these detailed aspects, will ensure that your Threadfin Rainbowfish thrive and continue to add a splash of color and life to your aquarium.

Tank Maintenance for Threadfin Rainbowfish

Proper tank maintenance ensures a healthy environment for your Threadfin Rainbowfish. It’s not just about creating an ideal habitat but also about keeping it clean and healthy.

Here’s what you need to consider for pristine tank maintenance.

Regular Water Changes

Maintaining pristine water conditions is essential for the well-being of Threadfin Rainbowfish. Regular water changes are a must. Aim to replace 25% to 30% of your tank’s water every two weeks.

This process helps remove toxins and replace depleted minerals, contributing to the health of your vibrant inhabitants.

Cleaning the Tank and Decorations

Over time, algae and leftover food can accumulate in your tank and on decorations, leading to a murky environment. To avoid this, conduct monthly cleaning of the tank and its decorations.

Use an algae scraper or pad for the tank’s inner walls and a bleach solution (make sure to rinse thoroughly afterwards) for decorations.

Filter Maintenance

A clean filter ensures efficient operation and optimal water quality. Inspect your filter monthly for blockages or debris buildup and clean as needed.

Always replace filter media according to the manufacturer’s guidelines to ensure that it functions at its best.

Monitor Fish Health

Monitoring the health of your Threadfin Rainbowfish is as vital as maintaining the tank. Observe your fish regularly for any changes in their behavior, appearance, or eating habits. Promptly isolate and treat any fish displaying signs of illness.

The key to successful tank maintenance is regularity and keen observation. With the right care, your Threadfin Rainbowfish can live a healthy, vibrant life in your well-maintained aquarium, bringing joy and beauty to your home or office.

Acclimating Threadfin Rainbowfish

Introducing Threadfin Rainbowfish to their new home involves a careful acclimation process. Ensuring a smooth transition helps reduce stress and potential health issues.

Start by floating the bag your fish came in, still sealed, on the surface of your aquarium water. This allows the water inside the bag to gradually match the temperature of your tank over a period of 15-20 minutes.

After temperature acclimation, slowly introduce some tank water into the bag, about a cup every 10 minutes. This step allows the fish to get used to your tank’s water chemistry.

After an hour, you can use a net to gently transfer the fish into the tank. Avoid adding bag water into your tank to prevent potential contamination.

Threadfin Rainbowfish Diet and Feeding

Threadfin Rainbowfish thrive on a diverse diet. Here’s how to ensure they get the nutrients they need.

Variety is Key

Threadfin Rainbowfish are omnivorous, so their diet should include both plant-based and meat-based food. Variety in their diet enhances their health and color vibrancy.

Live and Frozen Foods

Consider offering live or frozen foods such as brine shrimp, daphnia, and bloodworms. These choices provide a rich source of protein, which is essential for their growth and health.

Vegetable Matter and Dry Foods

Threadfin Rainbowfish also enjoy vegetable matter. Algae-based flake foods, spirulina tablets, and blanched vegetables like peas and zucchini can be great additions to their diet.

Feeding Frequency

Feed your Threadfin Rainbowfish two to three times a day, providing only as much food as they can consume within three minutes. Overfeeding can lead to poor water quality and health issues.

With a careful acclimation process and a diverse, well-balanced diet, your Threadfin Rainbowfish can thrive, showcasing their vibrant colors and energetic personalities for all to see.

Threadfin Rainbowfish Tank Mates

When it comes to choosing tank mates for your Threadfin Rainbowfish, peaceful, similarly-sized species are your best bet.

Here are some suitable companions:

  1. Small Tetras: Species like Silver Tip Tetras or Ember Tetras make great tank mates, as they are peaceful and non-competitive.

  2. Corydoras Catfish: These bottom dwellers won’t compete with Threadfins for space, making them excellent cohabitants.

  3. Rasboras: Harlequin rasbora or Chili Rasboras share the Threadfin’s peaceful demeanor, making for a serene tank environment.

  4. Small Danios: Zebra Danio or Celestial Pearl Danios can peacefully co-exist with Threadfins, enhancing your tank’s biodiversity.

  5. Dwarf Gouramis: Known for their calm temperament, Dwarf Gouramis can add a dash of color to your tank without upsetting your Threadfins.

  6. Shrimps and Snails: Invertebrates like Cherry Shrimps or Nerite Snails are great choices, as they maintain a peaceful environment and help control algae.

On the other hand, some species aren’t suited for cohabitation with Threadfin Rainbowfish.

To avoid, consider:

  1. Cichlids: Except for dwarf species, most Cichlids can be aggressive and territorial.

  2. Large Barbs: Species like Tiger Barbs may nip at the Threadfin’s long fins.

  3. Big Catfish: Larger species may see Threadfins as prey.

  4. Arowanas and Oscars: These large predatory fish can harm Threadfins.

  5. Bettas: Known fin-nippers, Bettas could stress and harm your Threadfins.

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Breeding Threadfin Rainbowfish and Fry Care

Breeding Threadfin Rainbowfish can be a rewarding experience. Follow these steps to encourage successful spawning and ensure proper fry care:

Spawning Conditions

  1. Sexual Maturity: Threadfins usually reach sexual maturity at around 9-12 months. The males exhibit longer threads on their dorsal and anal fins.

  2. Water Parameters: Keep the temperature slightly higher, around 28°C (82°F). A slightly acidic pH (6.5-7) can also help induce breeding.

  3. Diet: Provide a high-quality diet rich in live and frozen foods to condition the fish for breeding.

Spawning and Fry Care

  1. Spawning: Male Threadfins court females by displaying their impressive fins. After eggs are laid and fertilized, they adhere to plants or spawning mops.

  2. Separation: Once spawning is over, consider removing adults to prevent them from eating the eggs.

  3. Hatch Time: Eggs typically hatch in 7-10 days.

  4. Fry Food: Newly hatched fry can be fed infusoria or commercially available fry foods. As they grow, introduce micro worms or baby brine shrimp.

Observing the growth of new life in your tank can be an exhilarating experience. Patience and careful observation will ensure your Threadfin Rainbowfish fry thrive.

Spotting Stress in Threadfin Rainbowfish

Threadfin Rainbowfish, like any living creatures, show signs when they’re stressed.

Here are common indications to look out for:

  1. Erratic Swimming: If your Threadfins are darting around the tank or swimming near the surface gasping for air, it could be a sign of stress.

  2. Loss of Color: Threadfins are vibrant fish. A pale or dull appearance may signal discomfort.

  3. Loss of Appetite: If your Threadfins are refusing their meals, it’s time to pay attention.

  4. Fin Clamping: Threadfins displaying clamped fins could be indicating stress or illness.

  5. Frequent Hiding: While these fish are typically active, excessive hiding may be a sign they’re not feeling well.

Threadfin Rainbowfish: Health Issues and Treatment

Common health issues in Threadfin Rainbowfish include:

  1. Ich: Also known as white spot disease, Ich is common in aquarium fish. Treat it with an Ich medication following manufacturer’s instructions.

  2. Fin Rot: If your Threadfins’ fins look ragged or have white edges, they may have fin rot. A course of antibiotics can usually address this.

  3. Fungal Infections: These manifest as cottony growths on your fish. Antifungal medications can help.

Remember, prevention is better than cure. Maintaining good water quality is the first line of defense against diseases.

Top Tips for a Healthy Aquarium

Keep your aquarium healthy with these additional tips:

  1. Consistent Routine: Stick to a regular schedule for feeding, cleaning, and maintenance.

  2. Monitor Water Parameters: Regularly check pH, temperature, and nitrate levels to ensure they’re within the appropriate range.

  3. Quarantine New Fish: To prevent disease spread, quarantine new fish before adding them to the tank.

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Is the Threadfin Rainbowfish Right for Your Aquarium?

Threadfin Rainbowfish could be a great addition to your tank, particularly if you value peaceful, colorful, and active fish. They thrive in well-maintained aquariums with plenty of plants and room to swim.

If you can meet these requirements, and enjoy observing their unique social behavior, the Threadfin Rainbowfish could be the perfect choice for your aquarium!

Threadfin Rainbowfish Conservation Status

As of my knowledge, The conservation status of the Threadfin Rainbowfish (Iriatherina werneri) hasn’t been evaluated by the IUCN Red List of Threatened Species.

That said, their populations are believed to be relatively stable, thanks to their widespread distribution across New Guinea and Northern Australia.

Availability and Pricing

Threadfin Rainbowfish, although not as common as some other species in pet stores, can often be found in well-stocked aquarium shops and online.

The price can vary based on size and coloration, but generally, they’re affordable. As of 2021, expect to pay between $5 to $10 per fish. Remember, it’s crucial to buy from reputable sellers to ensure you’re getting healthy, ethically sourced fish.

Frequently Asked Questions About Threadfin Rainbowfish

Q1: How many Threadfin Rainbowfish can I keep in my tank?

A1: As social fish, Threadfins prefer groups. Aim for a minimum of six. Remember, they need adequate space, so factor that into your tank size.

Q2: Can Threadfin Rainbowfish live with other species?

A2: Yes, as long as they are peaceful and require similar water conditions.

Q3: How long do Threadfin Rainbowfish live?

A3: With good care and ideal conditions, they can live for up to 5 years.


Threadfin Rainbowfish are a joy to behold with their vibrant colors and graceful fins. Ideal for hobbyists seeking a peaceful, social, and relatively easy-to-care-for fish, Threadfins can add a dash of charm to your aquarium.

With the right conditions and care, these fish will reward you with years of delightful viewing.

Remember, whether you’re a novice or experienced aquarist, maintaining an aquarium is a commitment that requires time, care, and a deep appreciation for the aquatic world.

So, embark on your Threadfin Rainbowfish journey with confidence, backed by the wealth of knowledge provided in this guide.