Threadfin Rainbowfish care guide
Threadfin Rainbowfish (Iriatherina werneri) — minimum tank 40 L, temperature 24-30 °C, pH 5.5-7.5.
Compiled by Aquairi from published sources · Published · Updated
Overview
The Threadfin Rainbowfish (Iriatherina werneri) is a small melanotaeniid from northern Australia and New Guinea. Males display dramatically elongated thread-like dorsal and anal fin rays; both sexes show subtle iridescent body colour.
Taxonomy
- Family: Melanotaeniidae
- Genus: Iriatherina
- Scientific name: Iriatherina werneri
- Common synonyms: Featherfin Rainbowfish
Habitat
Native to vegetated swamps, billabongs and slow-flowing creeks of northern Australia (Cape York Peninsula) and southern New Guinea, in warm, soft to moderately hard, slightly acidic to neutral water.
Tank requirements
- Minimum tank volume: 40 L (10.6 US gal)
- Adult size: 3-4 cm
- Temperature: 24-30 °C (75-86 °F)
- pH: 5.5-7.5
- GH: 3-12 °dGH
- Water flow: low
- Lifespan: 3-5 years
- School size: ≥6 individuals
Diet
An omnivore with a small mouth. Offer finely crushed flakes, micro-pellets and small live or frozen foods (cyclops, daphnia, baby brine shrimp).
Compatibility
A peaceful, delicate shoaling species. Keep a group of at least six in a heavily planted aquarium with subdued lighting and gentle flow. Avoid all fin-nipping species (barbs, Serpae Tetra) and very active tankmates; ideal companions are calm nano fish such as Boraras, Ember Tetra and dwarf rasboras.
Breeding
An egg-layer that places adhesive eggs on fine-leaved plants or spawning mops over several days. Eggs incubate for 7-12 days; fry are tiny and require infusoria as a first food.
Threadfin Rainbowfish Breeding Guide
Overview
Iriatherina werneri is a small, delicate rainbowfish, reaching about 5 cm in body length excluding the elongated tail fin, found in freshwater swamps and thickly vegetated flowing waters of tropical northern Australia and New Guinea. It is notable for the dramatically elongated fins of the male and an elaborate breeding display. Females deposit a few eggs daily over an extended period rather than spawning all at once, so a colony in a well-planted tank can produce fry continuously.
Sexing
Adult males possess extended unpaired and pelvic fins and are larger and more colourful than females.
Breeding Setup
Two approaches work. In the isolation method, place a single male with two or three females in a smaller tank fitted with an air-powered sponge filter and a spawning medium of nylon mops or aquatic moss. In the colony method, keep a group of adults in a larger, fully decorated, well-planted setup that allows some fry to survive on their own.
Spawning Behavior & Trigger
Displaying males intensify their colouration, hold the rounded first dorsal fin erect, and use a flicking gesture of the filamentous rays of the second dorsal and anal fins to entice a mate, often under floating vegetation. Spawning occurs throughout daylight hours in warmer periods, and a single male may mate with several females in one day, with females depositing a few eggs daily for several days.
Egg & Fry Care
Eggs scattered among submerged vegetation hatch within roughly 7-10 days. Rear the fry with regular small water changes and feed them at least twice daily. Their extremely small size at first feeding is the principal difficulty of artificial rearing.
Common Challenges
The very small first-feeding fry are demanding to raise, and the male's delicate filamentous fins mean tankmates that nip fins must be avoided in any breeding group.