Threadfin Rainbowfish (Iriatherina werneri)

Transform your aquascape with the ethereal beauty of the Threadfin Rainbowfish. Known for their striking, feather-like fins and shimmering metallic bodies, these peaceful schooling fish are a centerpiece favorite for dedicated hobbyists and nano-aquarium enthusiasts alike.

Quick Care Overview

• Origin: Northern Australia, Indonesia, and Papua New Guinea

• Temperament: Very Peaceful / Shy

• Size: Up to 2 inches (5 cm)

• Minimum Tank Size: 15–20 Gallons

• Water Temperature: 73°F to 86°F

• pH Level: 6.0 – 7.5

Natural Habitat & Environment

Native to the slow-moving, heavily vegetated freshwater swamps and lagoons of Oceania, the Threadfin Rainbowfishthrives in "jungle" style setups. To make them feel at home, provide a densely planted aquarium with plenty of driftwood and floating plants to provide shade. Darker substrates will help their iridescent silver and neon-blue highlights truly pop.

Diet & Feeding

Despite their active nature, Threadfins have exceptionally small throats. They require micro-foods to thrive. We recommend a varied diet of:

• High-quality crushed flakes or micro-pellets.

• Live or frozen Baby Brine Shrimp (Artemia).

• Cyclops or Daphnia.

• Golden Pearls or other powdered fry foods.

Ideal Tank Mates

Because of their delicate fins and shy disposition, choose tank mates carefully. Avoid fin-nippers or aggressive species.

• Best matches: Other Rainbowfish species, Blue-eye Pseudomugils, peaceful Tetras (like Ember or Neon Tetras), Rasboras, Corydoras, and ornamental Shrimp (Neo-caridina).

Breeding the Threadfin Rainbowfish

Breeding Iriatherina werneri is a rewarding challenge. In a dedicated breeding tank with a spawning mop or fine-leaved plants like Java Moss, males will display vibrant colors and "flick" their long dorsal fins to attract females. They are continuous spawners, laying a few eggs daily. Note that the fry are microscopic and require infusoria or liquid fry food for the first several days.

Why Choose the Threadfin Rainbowfish?

If you are looking for a low-bioload fish that brings constant movement and a touch of "wild-type" elegance to a planted tank, the Threadfin is unmatched. Their unique swimming style and intricate finnage make them one of the most photographed species in the freshwater hobby.

PLEASE READ BEFORE ORDERING

• The photos shown on fish product pages are representations of adult fish and are NOT the actual fish that you will be receiving. 
• Please visit our “Ordering/Shipping fish” page prior to checking out to familiarize yourself with our process.
• We ship fish exclusively using overnight shipping with either FedEx or UPS. We will not ship fish with lesser expensive shipping services like “Ground” or “Priority Mail”. This is to ensure the safety of the fish. 
• Unless specified, all fish are sold as unsexed.