Threadfin Rainbow (Iriatherina werneri) – Graceful Beauty with Flowing Fins

The Threadfin Rainbow (Iriatherina werneri) is a delicate and elegant freshwater species admired for its long, flowing fins and shimmering iridescent body. Males are especially striking, displaying extended filament-like dorsal and anal fins and soft hues of gold, blue, and even red tones when fully mature and healthy.

Native to slow-moving streams and swamps in northern Australia and New Guinea, the Threadfin Rainbow thrives in peaceful, planted aquariums with gentle filtration and soft, acidic water. Though small in size, their unique appearance and graceful swimming make them stand out in nano and community tanks alike.

Key Features:

• Latin Name: Iriatherina werneri

• Common Name: Threadfin Rainbow

• Coloration: Iridescent body with elongated, flowing fins (males); subtle colors with elegant form

• Temperament: Peaceful and shy

• Size: Up to 2 inches

• Tank Requirements: Minimum 15 gallons, with dense plants, calm water, and low flow

• Diet: Omnivorous—micro pellets, powdered flakes, live/frozen foods like baby brine shrimp and daphnia

• Compatibility: Best with other peaceful, non-fin-nipping fish; ideal for planted nano tanks

Tips:

• Keep in groups of 6 or more, with a good male-to-female ratio to reduce stress.

• Avoid boisterous or aggressive tank mates that may nip their long fins.

• Use sponge filters or gentle flow to protect their delicate fins.

• Enhance colors with a protein-rich diet and stable water conditions.

Why Choose This Fish?
The Threadfin Rainbow offers a perfect blend of beauty, subtlety, and tranquility. Its feather-like fins and elegant movement make it an ideal choice for peaceful planted aquariums or aquascapes, especially for hobbyists seeking something graceful, refined, and utterly unique.