

The Threadfin Rainbowfish (Iriatherina werneri), also known as the Featherfin Rainbowfish, is a delicate and visually stunning freshwater species native to northern Australia and New Guinea. Renowned for its elongated, flowing fins and iridescent body, this peaceful fish is an excellent addition to well-planted nano aquariums. Males display vibrant colors and intricate fin extensions, especially during courtship displays, making them a captivating centerpiece in any community tank.
Species: Iriatherina werneri
Common Names: Threadfin Rainbowfish, Featherfin Rainbowfish
Size: Up to 5 cm (2 inches)
Lifespan: 3 to 5 years
Temperament: Peaceful and social; thrives in groups of 6 or more
Diet: Omnivorous; prefers small live foods like Daphnia, Artemia nauplii, micro worms, and copepods; can also accept finely crushed flake foods and micro pellets
Water Parameters:
Temperature: 22°C to 30°C (72°F to 86°F)
pH Level: 5.0 to 7.5
Hardness: 3 to 10 dGH
Exquisite Appearance: Males exhibit elongated dorsal and anal fins with vibrant coloration, creating a graceful display in the aquarium.
Peaceful Nature: Ideal for community tanks with other small, non-aggressive species.
Active Schooling Behavior: Thrives in groups, displaying natural schooling behavior that adds dynamic movement to the tank.
Compact Size: Suitable for nano and small aquariums due to their small size and minimal bioload.
Minimum Tank Size: 60 cm (24 inches) in length; approximately 54 liters (15 gallons)
Aquascape: Densely planted with both rooted and floating plants; inclusion of driftwood and gentle water flow is recommended
Lighting: Moderate lighting to enhance coloration and mimic natural habitat
Filtration: Gentle filtration to maintain water quality without creating strong currents.
Due to their peaceful nature and delicate fins, Threadfin Rainbowfish should be housed with similarly gentle species:
Pygmy Corydoras (Corydoras pygmaeus)
Otocinclus Catfish (Otocinclus spp.)
Small Rasboras (Boraras spp.)
Dwarf Shrimp (Caridina and Neocaridina species)
Other small, non-aggressive fish
Avoid housing with fin-nipping or overly active species to prevent stress and fin damage.
Diet: Provide a varied diet consisting of high-quality micro pellets, finely crushed flake foods, and small live or frozen foods such as Daphnia, Artemia nauplii, and micro worms.
Feeding Frequency: Feed small amounts 2–3 times daily, ensuring all food is consumed promptly to maintain water quality.
Water Quality: Maintain stable water parameters with regular partial water changes (20–25% weekly).
Tank Maintenance: Regularly clean the substrate and remove any uneaten food to prevent ammonia spikes.
Observation: Monitor for signs of stress or disease, such as faded coloration or clamped fins, and address any issues promptly.
Can Threadfin Rainbowfish be kept in a community tank?
Yes, they are peaceful and do well with other small, non-aggressive species.
Do they require a heater?
Yes, maintaining a stable temperature between 22°C to 30°C (72°F to 86°F) is essential for their health.
How often should I feed my Threadfin Rainbowfish?
Feed small amounts 2–3 times daily, ensuring all food is consumed within a few minutes.
Are they suitable for beginners?
While they are peaceful and small, their specific dietary and water quality needs make them more suitable for aquarists with some experience.
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