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Featherfin Rainbowfish (Iriatherina werneri)

Photo of: Featherfin Rainbowfish (Iriatherina werneri)

Scientific Name(s): Iriatherina werneri


Common Name(s): Featherfin Rainbowfish, Threadfin Rainbowfish, Feather Fin Rainbow Fish


Family: Melanotaeniidae


Species Type: Rainbowfishes


Maximum Size: 2 inches


Life Span: 3 years


Natural Habitat: Austrailian Rivers and Streams.


Minimum Tank Size: 20 gallons


Tank Region: Middle to top of tank.


Possible Tank Mates: Other peaceful community fish


Description: The Threadfin Rainbowfish (Iriatherina werneri) was described by Meinken in 1974 and is the only species currently recognized within its genus. They have been a popular aquarium fish with Australian native fish enthusiasts for many years and are easy to maintain under standard aquarium conditions. However, they are best kept by themselves or in a suitable community aquarium containing small blue-eye species such as Pseudomugil gertrudae or Pseudomugil tenellus. A breeding tank can be easily set up and the fish induced to spawn throughout the year. Although, some aquarists have found this species has been a difficult challenge to successfully raise the newly hatched larvae.
Iriatherina werneri may reach a maximum size of 2 inches, but are usually less than 1.5 inches. Mature males have a first dorsal fin that is fan shaped, while the second dorsal fin has exceptionally long filaments. The anal fin is similarly extended. This elegant finnage is used in a remarkably vivacious display for females and rival males. The body is slender, laterally compressed and general metallic silver with slightly visible dark vertical bars. The colors of the dorsal, anal and pelvic fins are black with a reddish-tan wash. The tail fin is deeply forked, transparent, and edged in a rustic red coloration. There are also small differences in fin shape and coloration of some male specimens from different locations. Some males have a narrow and high sail-like first dorsal fin, while this fin is lower and broader in other males. Females pale in comparison to the males, although their tail fins are adorned with a pinkish margin and the edges of the pelvic and anal fins are edged with black. Coloration in the wild is usually much more intense than when maintained in the confines of an aquarium. Specimens found in New Guinea are usually darker than the Australian variety.


Temperature Range: 78°F - 86°F



pH Range: 6.2 - 8

pH 5.0
pH 6.0
pH 7.0
pH 8.0
pH 9.0


Hardness Range: 5° - 15°



Breeding Information: Unlike many hardier rainbows, they can't be counted upon to breed themselves. Near-immaculate conditions, a slight cooling and a decent-sized water change may induce spawning behaviours. Males start the spawning process by displaying to the females and the spawning almost always takes place in the morning (though you can likely affect the time of spawning by changing the times at which the fish room is light). These fish will likely have eggs attached to plants. They may be induced to use a spawning mop but there is no guarantee that they would choose that over other plants in the tank. Microencapsulated fry foods are good starter foods, as are microworms. Anything much larger can and may cause serious damage to a fish whose mouth is large but throat is not.


Sexing Information: Males tend to have larger, more elaborate finnage than females.


Diet: Omnivorous - Does well with floating pellet or flake foods.


Temperament: Peaceful schooling fish


Common Diseases: None specific to species, but does require very good water quality.


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Keith Pardee

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