Threadfin Rainbow

Threadfin Rainbowfish (Iriatherina werneri)

The Threadfin Rainbowfish is a delicate and elegant nano fish, admired for its elongated filament-like fins, shimmering body coloration, and graceful movements. Native to the slow-moving streams, swamps, and wetlands of northern Australia and New Guinea, this unique rainbowfish is treasured by aquarists for its refined beauty, peaceful temperament, and fascinating display behaviors. Its flowing finnage and gentle presence make it a stunning addition to planted and specialty aquariums.

Threadfin Rainbowfish are calm, social fish that thrive when kept in groups, where males showcase their spectacular fins through graceful courtship displays. Males develop extended dorsal, anal, and pelvic fin rays, often displaying these features while competing harmlessly with one another and impressing females. They spend most of their time in the middle and upper levels of the aquarium and are best kept with other peaceful nano fish that will not outcompete them for food.

These elegant rainbowfish thrive in mature, well-planted aquariums with gentle filtration, subdued lighting, and plenty of cover. Floating plants, fine-leaved vegetation, and open swimming areas help recreate their natural habitat while allowing their delicate finnage to be fully appreciated. Because of their small size and gentle feeding habits, they benefit from a varied diet of appropriately sized foods, including crushed flakes, micro pellets, baby brine shrimp, daphnia, and other small frozen or live foods to maintain their health and coloration.

Quick Facts:

• Care Level: Moderate
• Temperament: Peaceful
• Adult Size: 1.5–2 inches (4–5 cm)
• Minimum Tank Size: 10 gallons
• Temperature: 72–82°F (22–28°C)
• pH: 5.5–7.5
• Diet: Omnivore
• Schooling: Yes, best kept in groups of 6 or more

With their graceful thread-like fins, gentle personality, and captivating display behaviors, Threadfin Rainbowfish are an exceptional choice for aquarists seeking a unique nano species that adds elegance, movement, and a touch of sophistication to planted freshwater aquariums.