Forktail rainbowfish

The forktail blue-eye is a small, peaceful rainbowfish relative endemic to the rainforest streams of eastern Papua New Guinea. SeriouslyFish gives a maximum standard length of 40–60 mm, with males reaching the upper end of that range and developing bright yellow unpaired fins edged in black, a forked caudal fin, and a metallic blue sheen across the upper body. Females are plainer but still attractive, with a silvery-yellow body and translucent fins. Every fish in the aquarium trade today traces back to a single collection in 1981 — no wild specimens have been exported since, and the resulting inbreeding has produced some reduced fertility and shortened lifespans. A 54-litre tank with a 60×30 cm base is sufficient for a small group, but these are active shoaling fish that need space to display. The tank should be densely planted with floating cover to diffuse the light, and water movement should be moderate. Water parameters need to be on the hard, alkaline side: pH 7.0–8.0 and temperature 24–28°C. They are sensitive to poor water quality and chemistry swings, so the aquarium must be mature and stable before introducing them. Diet consists mainly of small live and frozen foods such as Daphnia, Moina, and Artemia, though crushed floating flakes are accepted once the fish learn to take them. Keep them in groups of at least eight to ten; males display continuously to one another in a fascinating, non-aggressive competition of fin-spreading and posturing. Breeding is possible but eggs take about three weeks to hatch, and the fry are minute. The species has a relatively short lifespan, with fecundity declining after 12–18 months.