Threadfin Rainbowfish (Iriatherina werneri) is a delicate and peaceful freshwater fish prized for its long, flowing fin extensions and shimmering colors. It is ideal for community aquariums with gentle water flow and calm tankmates.
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Threadfin Rainbowfish (Iriatherina werneri) is a delicate and peaceful freshwater fish prized for its long, flowing fin extensions and shimmering colors. It is ideal for community aquariums with gentle water flow and calm tankmates.
Slender, laterally compressed body with long, thread-like extensions on the dorsal and anal fins. Body color ranges from silvery-blue to light green with hints of iridescent sheen. Males have more pronounced and elongated fins; females are smaller with shorter fins.
3–5 years with proper care
Omnivorous; feeds on high-quality micro pellets, flakes, frozen foods, and live foods such as baby brine shrimp, daphnia, and micro worms. Occasional finely chopped vegetables can supplement nutrition.
Threadfin Rainbowfish are ideal for aquarists seeking delicate, peaceful, and visually captivating schooling fish. Their long fins and shimmering colors make them a standout in planted aquariums.
Intermediate – requires stable water, proper schooling, gentle tankmates, and high-quality nutrition.
15+ gallons (for small school)
6.5 to 7.5
5–12 dGH
72–78°F (22–26°C)
1.5 inches
Small tetras, rasboras, dwarf gouramis, micro rasboras, peaceful danios. Avoid aggressive or large species.
Aggressive, fast, or nippy fish. Avoid large or boisterous species that may outcompete or stress them.
Iriatherina werneri
Melanotaeniidae
Northern Australia and Papua New Guinea – slow-moving or still waters with dense vegetation.
Highly social; best kept in schools of 6 or more. Extremely peaceful and compatible with other small, gentle community fish.
Feed 2–3 times daily with flakes, micro pellets, frozen/live foods. Ensure small particle sizes suitable for their tiny mouths.
Egg-scatterer; deposits eggs among fine-leaved plants. Adults do not guard eggs. Condition males and females with high-protein live foods before spawning. Fry feed on infusoria or baby brine shrimp.
pH: 6.5–7.5, Temperature: 72–78°F (22–26°C), Hardness: 5–12 dGH, Ammonia/Nitrite: 0 ppm, Nitrate: <20 ppm
Prone to stress and fin damage if kept with aggressive species. Sensitive to poor water quality and sudden parameter changes. Maintain stable conditions and high-quality diet.
Extremely peaceful and shy. Best kept in schools of 6 or more to reduce stress and encourage natural behavior. Avoid aggressive or fast-swimming tankmates.
Native to northern Australia and Papua New Guinea, Threadfin Rainbowfish inhabit slow-moving or still waters with dense vegetation. Adults grow up to 1.5 inches. A small, heavily planted tank with gentle water flow, floating plants, and stable parameters is essential. They are sensitive to water quality changes and require consistent care. Ideal for intermediate aquarists seeking peaceful, schooling, and aesthetically delicate species.