Forktail Rainbowfish
Pseudomugil furcatus
Pseudomugilidae
About
A roughly 5 cm blue-eye from the lowland rainforest streams of eastern Papua New Guinea, restricted in the wild to the Musa and Kwagila drainages between Dyke Ackland and Collingwood Bays. Every specimen in the hobby is captive-bred and traces back to a single 1981 collection. Males show a grey-green flank, luminous blue eyes and yellow-edged fins, with the forked tail tipped in yellow; they spar in tight circles and flare their fins to impress females. Fast, restless and never still, the shoal patrols the upper half of the tank all day.
Care
Keep a group of at least 8-10 in a mature, densely planted tank of 60 L or more with a 60 cm footprint, and fit a tight lid — they are committed jumpers. Target 24-27 °C, neutral to alkaline pH 7.0-8.0 and moderately hard water around 5-25 dGH, well oxygenated with gentle to moderate flow. This species dislikes swings in chemistry, so never add it to a biologically immature aquarium. Even in good conditions expect only 2-3 years, and reduced fertility after 12-18 months.
Diet
Offer several small meals a day of finely sized floating or suspended foods. Live and frozen daphnia, moina, cyclops, Artemia nauplii and microworm bring out the best colour; nano pellets, micro pellets and crushed flake work as the everyday staple. Watch feeding in a community tank, as slower or larger fish may take everything before the shoal gets its share.
Tankmate compatibility
Gets along with (35)
Possible with care (179)
Avoid (57)
Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.
Telling males from females
What works for this species, most reliable first.
- Colour and patternStrong · from about 6 months, and only on a settled fish
In rainbowfish, killifish and several barbs the male carries the colour — deeper and more saturated, intensifying further when he displays.
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Frequently asked questions
- What tank size does a Forktail Rainbowfish need?
- A Forktail Rainbowfish needs an aquarium of at least 60 litres (15.9 US gallons) with a footprint at least 60 cm (23.6 in) long — for this species, swimming length matters as much as raw volume.
- What water parameters does a Forktail Rainbowfish need?
- Forktail Rainbowfish does best at 23–28 °C (73.4–82.4 °F), pH 6.5–8 and a general hardness of 5–25 °dGH.
- What group size does a Forktail Rainbowfish need?
- Forktail Rainbowfish is a social species — keep a group of at least 8 so natural behaviour emerges and stress stays low.
- Is the Forktail Rainbowfish suitable for beginners?
- Yes — Forktail Rainbowfish is one of the easier species to keep and forgives typical first-tank mistakes, as long as the aquarium is cycled and maintained.