Threadfin Rainbow
Iriatherina werneri

Care Level




Reef Compatible


Plant Safe


Max Size

Less than 2"

Minimum Tank Size

20 gallon


Black, Blue, Grey, Red, Silver, Yellow



Water Conditions

Acidic (5.2-7.5 pH), soft water (3 to 6 dGH), 72 to 82 degrees Fahrenheit


General: The Threadfin Rainbowfish Iriatherina werneri can live three to five years in captivity, and reach a length of up to two inches. They require a tank size of 15 gallons, or larger. This species is best kept in schools with a 3:1, male to female ratio. The males will commonly flare their dorsal fins to assert dominance, and there are minimal amounts of physically harmful aggression. The Threadfin Rainbowfish will typically stay in the upper-half of the water column.

Fecundity: The Threadfin Rainbowfish will commonly produce over 20 fry. It is easiest to find two healthy females, and add a colorful male to a small, highly oxygenated aquarium. This species naturally reproduces in floating vegetation so it is best to mimic those conditions. After spawning has occured, seperate the adults as they will be willing to consume the eggs. During the breeding season, water temperature will be approximately 78 degrees Ferenheit.

Habitat: Slow-moving, clear, and shallow waters of Indonesian, and Australian river mouths. Regardless of region, these fish will greatly prefer areas with floating woody debris, and vegetation.

Preferred Water Chemistry: This species will benefit, and display best color in slightly acidic (5.5 to 7.5), and intermediate water hardness (5 to 15dGH) conditions. They prefer minimal amounts of current, and will benefit from stable water chemistry (frequent, but minor water changes < 10%). Aquarium Diet (omnivorous): The Threadfin Rainbowfish has a very small mouth. Naturally, they will feed on diatoms, algae, and very small insects. In aquaria, they should be fed a varied diet of daphnia, brine shrimp, copepods, and blackworms. Dimorphism: The male Threadfin Rainbowfish will have elongated anterior, and posterior dorsal fins. The male will also elongated pelvic, and anal fins. Males will display a variety of colors based on living conditions. After maturation, females will stay honey, silver, and green in coloration. They will also have short fins, in comparison to the male.

Threadfin Rainbow Photo Gallery

Threadfin Rainbow Videos

Author: Aquatics Unlimited