Pseudomugil furcatus
Tiny rainbowfish with electric blue eyes and yellow-edged forked tail. Males spar constantly with fins flared but never harm each other, pure display. Excellent for nano planted scapes with cherry shrimp and otocinclus.
Forktail Blue-Eye (Pseudomugil furcatus) reaches 4–5 cm as an adult and needs a minimum tank of 60 L. Native to Papua New Guinea, it lives in the mid to top water column with a peaceful temperament. Aim for 23–27 °C, pH 6.5–7.5, and 5–15 dGH hardness. Lifespan is 2–3 years with good care. Keep forktail blue-eye in groups of 6+, yes schoolers need numbers to display natural behaviour. Diet: micropredator, Micro pellets, baby brine shrimp, daphnia, mosquito larvae. Plant-safe: Yes. Shrimp-safe: Yes (adult shrimp).
Care at a glance
Tiny rainbowfish with electric blue eyes and yellow-edged forked tail. Males spar constantly with fins flared but never harm each other, pure display. Excellent for nano planted scapes with cherry shrimp and otocinclus.
By Mike ElmiraUpdated 2 min read
Part of our complete guide to aquarium fish for the planted tank.
The parameters that decide whether forktail blue-eye fits in your tank.
Mid to Top
Yes
Group of 6+
Pseudomugilidae
Micropredator
Micro pellets, baby brine shrimp, daphnia, mosquito larvae.
2–3 yrs
Easy
Shallow rainforest streams of West Papua
Papua New Guinea
Tank-mate safety and the species this one is documented to thrive (or fail) alongside.
Other peaceful nano fish: ember tetras, chili rasboras, sparkling gouramis, otocinclus, cherry shrimp adults, threadfin rainbowfish (same family habits).
Aggressive fish, fin-nippers, anything large or predatory.
Hard-won lessons from the tank.
Two males in the same tank produce near-constant fin-display sparring (pure show, no real aggression) — one of the most active displays of any nano fish. Pair with a heavily planted tank with floating plants for the species to look its best. The blue eye colour intensifies when keeping conditions are right; pale eyes signal stress.
Genus 'Pseudomugil' = 'false mullet' (resembling marine mullets despite being freshwater). Species 'furcatus' = 'forked' for the deeply-forked caudal fin.
What can go wrong and how to spot it.
Failure modes, in order of how dramatic the fix is.
Sensitive to nitrate above 20 ppm and parameter swings. Standard nano-fish susceptibilities.
Often confused with neon tetras — the iridescent blue eye is the giveaway. Forktail blue-eyes are pseudomugils, not characins, and prefer slightly harder water than neons.
The practical routine, read top to bottom.
60 L+. Heavy planting with open mid-water swimming. Moderate-flow well-oxygenated water. Sand or fine gravel. Warm temperature.
2–3 weeks.
Where it comes from, how it behaves, and the variants you'll see at retail.
Where it lived before it came home.
Forest streams and pools in eastern Papua New Guinea. Soft to moderately hard, neutral to slightly alkaline, clean well-oxygenated water with dense edge vegetation.
Insect larvae, small crustaceans, biofilm. Mid- and upper-water column feeders.
Not threatened. Captive-bred globally; wild-caught specimens are uncommon.
How they pair, reproduce, and grow.
Males have intense yellow-edged fins and bright blue-ringed eyes. Females have similar eyes but plainer fins. Both sexes share the silver body and forked tail.
Continuous spawners among Java moss. Eggs hatch in 10–14 days; fry are tiny and need infusoria initially. A planted colony tank self-sustains with regular fry survival.
The named cultivars and the lookalikes worth flagging.
Wild type. Several Pseudomugil species are sold under 'blue eye' labels: P. furcatus (this species), P. luminatus (red neon blue-eye), P. signifer (Pacific blue-eye), P. gertrudae (spotted blue-eye). All similar care.
Direct answers to the questions search engines and AI assistants surface most often about this species.
Forktail Blue-Eye (Pseudomugil furcatus) needs a minimum tank of 60 L. They live in the mid to top water column and should be kept in groups of 6+, so a longer footprint matters more than depth.
Target 23–27 °C, pH 6.5–7.5, and 5–15 dGH hardness. Acclimate slowly when moving them between water sources.
Shrimp safety: Yes (adult shrimp). Plant safety: Yes.
Forktail Blue-Eye are micropredator. Micro pellets, baby brine shrimp, daphnia, mosquito larvae.
On Fin & Stem's 1–5 difficulty scale this species rates 2/5. Forgiving, beginner-friendly once the tank is cycled. Breeding difficulty: easy.
Typical lifespan in a well-maintained tank is 2–3 years.
A planted tank is a system. Pair this fish with one entry from each other pillar to plan the whole scape.
