Photo: Guérin Nicolas (messages) (CC BY-SA 3.0) — via Wikimedia Commons
Forktail Blue-eye (Pseudomugil furcatus)
A jewel-sized schooling fish with electric-blue eyes and forked, saffron-edged fins that shimmer in a heavily planted nano tank.
Will it live with a Forktail Blue-eye?
We compare each fish against your forktail blue-eye on temperament, size, water parameters and swimming zone. Set your tank size and filter the results.
- Adolf's Cory✅ CompatiblePeaceful · 5.5 cm · Medium care · 22–26 °C (72–79 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Adolf's Cory in a shoal of 6+ or it gets stressed and nippy.
- Axelrod's Cory✅ CompatiblePeaceful · 5 cm · Easy care · 23–28 °C (73–82 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Axelrod's Cory in a shoal of 6+ or it gets stressed and nippy.
- Bandit Corydoras✅ CompatiblePeaceful · 5 cm · Easy care · 22–27 °C (72–81 °F)
- Both are peaceful, and their water overlaps around 22–27 °C — no size, zone or temperament conflicts.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Bandit Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Bloodfin Tetra✅ CompatiblePeaceful · 5.5 cm · Easy care · 18–28 °C (64–82 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Bloodfin Tetra in a shoal of 6+ or it gets stressed and nippy.
- Blue Turbo Snail✅ CompatiblePeaceful · 5 cm · Medium care · 25–30 °C (77–86 °F)
- Both are peaceful, and their water overlaps around 25–28 °C — no size, zone or temperament conflicts.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Checkered Barb✅ CompatiblePeaceful · 5 cm · Easy care · 20–25 °C (68–77 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Checkered Barb in a shoal of 6+ or it gets stressed and nippy.
- Cherry Barb✅ CompatiblePeaceful · 5 cm · Easy care · 23–27 °C (73–81 °F)
- Compatible on the things that matter: shared water near 23–27 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Cherry Barb in a shoal of 6+ or it gets stressed and nippy.
- Cochu's Blue Tetra✅ CompatiblePeaceful · 5 cm · Medium care · 22–28 °C (72–82 °F)
- Compatible on the things that matter: shared water near 22–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Cochu's Blue Tetra in a shoal of 8+ or it gets stressed and nippy.
- Firehead Tetra✅ CompatiblePeaceful · 5 cm · Medium care · 24–28 °C (75–82 °F)
- Compatible on the things that matter: shared water near 24–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Firehead Tetra in a shoal of 8+ or it gets stressed and nippy.
- Five-banded Barb✅ CompatiblePeaceful · 5 cm · Easy care · 23–27 °C (73–81 °F)
- Both are peaceful, and their water overlaps around 23–27 °C — no size, zone or temperament conflicts.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Five-banded Barb in a shoal of 6+ or it gets stressed and nippy.
- Half-striped Penguin Tetra✅ CompatiblePeaceful · 5 cm · Medium care · 23–28 °C (73–82 °F)
- Compatible on the things that matter: shared water near 23–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Half-striped Penguin Tetra in a shoal of 6+ or it gets stressed and nippy.
- Harlequin Rasbora✅ CompatiblePeaceful · 5 cm · Easy care · 23–28 °C (73–82 °F)
- Compatible on the things that matter: shared water near 23–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Harlequin Rasbora in a shoal of 6+ or it gets stressed and nippy.
- Honey Gourami✅ CompatiblePeaceful · 5 cm · Easy care · 22–28 °C (72–82 °F)
- Compatible on the things that matter: shared water near 22–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Horseman Cory✅ CompatiblePeaceful · 5 cm · Medium care · 22–26 °C (72–79 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Horseman Cory in a shoal of 6+ or it gets stressed and nippy.
- Japanese Trapdoor Snail✅ CompatiblePeaceful · 5 cm · Easy care · 10–28 °C (50–82 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Julii Corydoras✅ CompatiblePeaceful · 5 cm · Easy care · 23–26 °C (73–79 °F)
- Compatible on the things that matter: shared water near 23–26 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Julii Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Masked Corydoras✅ CompatiblePeaceful · 5 cm · Easy care · 22–28 °C (72–82 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Masked Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Mystery Snail✅ CompatiblePeaceful · 5 cm · Easy care · 20–28 °C (68–82 °F)
- Both are peaceful, and their water overlaps around 22–28 °C — no size, zone or temperament conflicts.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Panda Corydoras✅ CompatiblePeaceful · 5 cm · Medium care · 20–26 °C (68–79 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Panda Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Rummy-nose Tetra✅ CompatiblePeaceful · 5 cm · Medium care · 23–29 °C (73–84 °F)
- Compatible on the things that matter: shared water near 23–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Rummy-nose Tetra in a shoal of 6+ or it gets stressed and nippy.
- Skunk Corydoras✅ CompatiblePeaceful · 5 cm · Easy care · 22–26 °C (72–79 °F)
- Compatible on the things that matter: shared water near 22–26 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Skunk Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Stoliczka's Barb✅ CompatiblePeaceful · 5 cm · Easy care · 20–26 °C (68–79 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Stoliczka's Barb in a shoal of 6+ or it gets stressed and nippy.
- Xingu Black Neon Tetra✅ CompatiblePeaceful · 5 cm · Medium care · 24–28 °C (75–82 °F)
- Compatible on the things that matter: shared water near 24–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Xingu Black Neon Tetra in a shoal of 8+ or it gets stressed and nippy.
- Zebra Danio✅ CompatiblePeaceful · 5 cm · Easy care · 18–25 °C (64–77 °F)
- Compatible on the things that matter: shared water near 22–25 °C, workable temperaments, and no predator-and-prey size gap.
- Both favour the top of the tank — offer enough cover so they aren't always in each other's space.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Zebra Danio in a shoal of 6+ or it gets stressed and nippy.
- Amano Shrimp⚠️ With cautionPeaceful · 5 cm · Easy care · 18–28 °C (64–82 °F)
- Forktail Blue-eye may eat Amano Shrimp or pick off its shrimplets — a densely planted tank with moss gives them a fighting chance.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Black Ruby Barb⚠️ With cautionSemi-aggressive · 6 cm · Easy care · 22–26 °C (72–79 °F)
- Expect Black Ruby Barb to harass Forktail Blue-eye at times; give dense cover and watch them at feeding.
- Your 75 L tank is below the ~100 L this pairing really wants — crowding raises aggression.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Black Ruby Barb in a shoal of 6+ or it gets stressed and nippy.
- Black Skirt Tetra⚠️ With cautionSemi-aggressive · 6 cm · Easy care · 20–26 °C (68–79 °F)
- Black Skirt Tetra is semi-aggressive and may chase or nip the smaller Forktail Blue-eye — plant heavily and break up sight lines.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Black Skirt Tetra in a shoal of 6+ or it gets stressed and nippy.
- Chocolate Gourami⚠️ With cautionPeaceful · 5 cm · Hard care · 25–30 °C (77–86 °F)
- Different pH ranges (6.5–8 vs 4–6); doable if you sit in the shared band, but not ideal long-term.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Chocolate Gourami in a shoal of 6+ or it gets stressed and nippy.
- Desert Goby⚠️ With cautionSemi-aggressive · 6 cm · Easy care · 18–28 °C (64–82 °F)
- Desert Goby and Forktail Blue-eye are close in size, but the semi-aggressive one tends to dominate — add forktail blue-eye in a group to spread the pressure.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Dwarf Chain Loach⚠️ With cautionPeaceful · 6 cm · Medium care · 24–29 °C (75–84 °F)
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Dwarf Chain Loach in a shoal of 6+ or it gets stressed and nippy.
- Eastern Betta⚠️ With cautionSemi-aggressive · 6 cm · Medium care · 24–28 °C (75–82 °F)
- Eastern Betta is semi-aggressive and may chase or nip the smaller Forktail Blue-eye — plant heavily and break up sight lines.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- GloFish Tetra⚠️ With cautionSemi-aggressive · 6 cm · Easy care · 21–28 °C (70–82 °F)
- GloFish Tetra is semi-aggressive and may chase or nip the smaller Forktail Blue-eye — plant heavily and break up sight lines.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep GloFish Tetra in a shoal of 6+ or it gets stressed and nippy.
- Humpbacked Tetra⚠️ With cautionSemi-aggressive · 5 cm · Hard care · 24–28 °C (75–82 °F)
- Humpbacked Tetra and Forktail Blue-eye are close in size, but the semi-aggressive one tends to dominate — add forktail blue-eye in a group to spread the pressure.
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Humpbacked Tetra in a shoal of 8+ or it gets stressed and nippy.
- Morse Code Corydoras⚠️ With cautionPeaceful · 5 cm · Medium care · 23–26 °C (73–79 °F)
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Morse Code Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Odessa Barb⚠️ With cautionSemi-aggressive · 6 cm · Easy care · 20–26 °C (68–79 °F)
- Odessa Barb and Forktail Blue-eye are close in size, but the semi-aggressive one tends to dominate — add forktail blue-eye in a group to spread the pressure.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Odessa Barb in a shoal of 6+ or it gets stressed and nippy.
- Peaceful Betta⚠️ With cautionSemi-aggressive · 6 cm · Medium care · 24–28 °C (75–82 °F)
- Expect Peaceful Betta to harass Forktail Blue-eye at times; give dense cover and watch them at feeding.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Silvertip Tetra⚠️ With cautionSemi-aggressive · 5 cm · Easy care · 22–28 °C (72–82 °F)
- Silvertip Tetra and Forktail Blue-eye are close in size, but the semi-aggressive one tends to dominate — add forktail blue-eye in a group to spread the pressure.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Keep Silvertip Tetra in a shoal of 6+ or it gets stressed and nippy.
- Spotfin Betta⚠️ With cautionSemi-aggressive · 5 cm · Medium care · 23–28 °C (73–82 °F)
- Spotfin Betta is semi-aggressive and may chase or nip the smaller Forktail Blue-eye — plant heavily and break up sight lines.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Striped Red-Eye Puffer⚠️ With cautionAggressive · 5 cm · Hard care · 24–28 °C (75–82 °F)
- Expect Striped Red-Eye Puffer to harass Forktail Blue-eye at times; give dense cover and watch them at feeding.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Wine Red Betta⚠️ With cautionAggressive · 5 cm · Medium care · 24–28 °C (75–82 °F)
- Water hardness preferences differ (Forktail Blue-eye 5–20 vs Wine Red Betta 0–4 dGH).
- Expect Wine Red Betta to harass Forktail Blue-eye at times; give dense cover and watch them at feeding.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Alligator Gar⛔ Not recommendedAggressive · 250 cm · Hard care · 24–28 °C (75–82 °F)
- Forktail Blue-eye is bite-sized to a 250 cm predatory alligator gar — it will be eaten.
- Expect Alligator Gar to harass Forktail Blue-eye at times; give dense cover and watch them at feeding.
- Your 75 L tank is below the ~3785 L this pairing really wants — crowding raises aggression.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Clown Knifefish⛔ Not recommendedAggressive · 90 cm · Hard care · 24–28 °C (75–82 °F)
- Size gap is too large (90 vs 5 cm): Clown Knifefish will treat Forktail Blue-eye as food.
- Clown Knifefish clearly outsizes Forktail Blue-eye and is aggressive; risky unless the tank is big and well-planted.
- Your 75 L tank is below the ~750 L this pairing really wants — crowding raises aggression.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Fire Eel⛔ Not recommendedSemi-aggressive · 100 cm · Medium care · 24–28 °C (75–82 °F)
- Fire Eel (100 cm) is big enough to swallow the 5 cm Forktail Blue-eye whole.
- Fire Eel clearly outsizes Forktail Blue-eye and is semi-aggressive; risky unless the tank is big and well-planted.
- Your 75 L tank is below the ~380 L this pairing really wants — crowding raises aggression.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Koi⛔ Not recommendedPeaceful · 90 cm · Medium care · 4–28 °C (39–82 °F)
- Koi (90 cm) is big enough to swallow the 5 cm Forktail Blue-eye whole.
- Your 75 L tank is below the ~3800 L this pairing really wants — crowding raises aggression.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Redtail Catfish⛔ Not recommendedAggressive · 120 cm · Hard care · 24–27 °C (75–81 °F)
- Redtail Catfish (120 cm) is big enough to swallow the 5 cm Forktail Blue-eye whole.
- Redtail Catfish is aggressive and may chase or nip the smaller Forktail Blue-eye — plant heavily and break up sight lines.
- Your 75 L tank is below the ~5700 L this pairing really wants — crowding raises aggression.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Spotted Gar⛔ Not recommendedAggressive · 90 cm · Hard care · 18–26 °C (64–79 °F)
- Forktail Blue-eye is bite-sized to a 90 cm predatory spotted gar — it will be eaten.
- Spotted Gar clearly outsizes Forktail Blue-eye and is aggressive; risky unless the tank is big and well-planted.
- Your 75 L tank is below the ~600 L this pairing really wants — crowding raises aggression.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Wels Catfish⛔ Not recommendedAggressive · 300 cm · Hard care · 15–25 °C (59–77 °F)
- Forktail Blue-eye is bite-sized to a 300 cm predatory wels catfish — it will be eaten.
- Expect Wels Catfish to harass Forktail Blue-eye at times; give dense cover and watch them at feeding.
- Your 75 L tank is below the ~20000 L this pairing really wants — crowding raises aggression.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Wolf Cichlid⛔ Not recommendedAggressive · 72 cm · Hard care · 24–30 °C (75–86 °F)
- Forktail Blue-eye is bite-sized to a 72 cm predatory wolf cichlid — it will be eaten.
- Expect Wolf Cichlid to harass Forktail Blue-eye at times; give dense cover and watch them at feeding.
- Your 75 L tank is below the ~760 L this pairing really wants — crowding raises aggression.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
Compatibility is computed from each species' care data — a strong starting point, not a guarantee. Individual temperament varies, so always introduce new fish slowly and watch them.
Forktail Blue-eye care specs
- Care level
- Easy
- Breeding
- Medium
- Max size
- 5 cm (2 in)
- Min tank size
- 60 L (15.9 gal)
- Temperature
- 22–28 °C (72–82 °F)
- pH
- 6.5–8
- Hardness
- 5–20 dGH
- Lifespan
- 3–5 years
- Diet
- Omnivore
- Swim level
- Top
- Group size
- 6+ (shoaling)
- Family
- Pseudomugilidae
- Origin
- Papua New Guinea — Milne Bay Province coastal streams and creeks
What is a Forktail Blue-eye?
The forktail blue-eye (Pseudomugil furcatus) is a micro-rainbowfish from Papua New Guinea’s Milne Bay Province, reaching only 4–5 cm (under 2 in). It belongs to the family Pseudomugilidae — the blue-eyes — distinct from the larger melanotaeniid rainbowfishes. Males carry vivid electric-blue eyes and bold yellow-to-saffron fin edging that intensifies during courtship; females share the blue irises but are otherwise subdued in colour.
Kept in a school of six or more against dark substrate and fine-leaved plants, they are one of the most rewarding sights in a nano planted tank. Care level is rated easy, making them accessible to newcomers and experienced keepers alike.
Where do forktail blue-eyes come from?
Wild forktail blue-eyes are endemic to Papua New Guinea — specifically the coastal streams, creeks and lowland waterways of Milne Bay Province. These habitats are clear to slightly tannin-tinted, with gentle current, dense marginal vegetation and a substrate of sand, fine gravel or leaf litter. Rainforest canopy keeps temperatures moderate and consistent. The result is a species that does not need warm tropical extremes and tolerates a broad range of water chemistry — from soft and slightly acidic to moderately hard and slightly alkaline.
What size tank do forktail blue-eyes need?
The minimum recommended tank size is 60 litres (15 gal), and this is genuinely workable provided the tank is well planted and the school is maintained. A longer aquarium footprint — 60 cm (24 in) or more — is preferable to a tall, narrow one, because forktail blue-eyes are top-level swimmers that spend most of their time in the upper third of the water column and need horizontal swimming space.
A tightly fitting lid is important: forktail blue-eyes will jump through even small gaps. Plant fine-leaved or feathery species — java moss, hornwort, ambulia or water wisteria — near the surface and midground to replicate Milne Bay stream vegetation and encourage confident schooling. Dark substrate and floating plant cover show off their coloration best.
Filtration should be gentle. A sponge filter or spray-bar outlet is ideal; strong current exhausts small fish and disrupts the slow fin-display courtship that makes the species so rewarding to watch.
What water parameters do forktail blue-eyes need?
- Temperature: 22–28 °C (72–82 °F). They are comfortable toward the cooler end of tropical ranges, which broadens their community compatibility.
- pH: 6.5–8.0 — a wide tolerance that covers soft-water and moderately hard setups alike.
- Hardness: 5–20 dGH. They adapt well to most municipal tap water within this range.
As with all small fish, stability matters more than perfection. A cycled tank, regular partial water changes (around 20–30% weekly), and a reliable heater are the foundations. Forktail blue-eyes are sensitive to ammonia and nitrite spikes — their small body mass gives them little buffer — so do not add them to an uncycled tank. Maintain nitrates below 20 ppm for long-term health and to keep colours vibrant.
What do forktail blue-eyes eat?
Forktail blue-eyes are omnivores that feed predominantly at the surface and upper water column. In the wild they take small invertebrates, zooplankton and the occasional algal material. In the aquarium they accept a varied diet without difficulty:
- Dry foods: Quality micro-pellets or finely crushed flake sized for fish under 5 cm. Standard community flake often needs to be powdered between the fingers before offering.
- Frozen foods: Baby brine shrimp, daphnia, cyclops, and micro worms are eagerly taken and excellent for conditioning.
- Live foods: Live baby brine shrimp and micro worms are especially valuable for bringing fish into breeding condition and for raising fry.
Feed small amounts two or three times per day — portions the fish can clear in two to three minutes. Overfeeding fouls the water quickly in a small tank. A varied diet keeps coloration at its best and supports immune function.
Are forktail blue-eyes peaceful — and what fish can they live with?
Forktail blue-eyes have a peaceful temperament and are excellent community fish, with a few practical caveats. They are a schooling species: a group of at least six is the minimum, and eight to ten or more produces noticeably better behaviour and more intense male display. A small group becomes timid, hangs near cover and rarely shows the fin-flaring courtship that makes the species worth keeping.
Because they reach only 5 cm (2 in), avoid housing them with anything predatory or boisterous enough to outcompete them at feeding. Ideal tank-mates occupy the mid- or lower water column: small corydoras, pygmy corydoras, otocinclus, and other peaceful nano species. They also pair well with dwarf shrimp (neocaridina, caridina) in a planted setup — adults are too small to threaten adult shrimp.
Avoid fin-nippers such as tiger barbs or serpae tetras, which will shred the males’ ornamental fins.
For a curated list of compatible species and pairings to avoid, see Forktail Blue-eye tank mates.
How do you tell male from female forktail blue-eyes?
Sexual dimorphism in forktail blue-eyes is clear in adults and useful for stocking decisions. Males develop:
- Elongated dorsal, anal and caudal fins with vivid yellow-to-deep-saffron edging along the margins.
- A distinctly forked (furcate) caudal fin with extended lobes — the feature that gives the species its common name.
- More intense overall body coloration, intensifying further during courtship.
Females are plainer: fins are shorter and rounded rather than elongated, the yellow-orange edging is absent or faint, and the body is a more uniform silver-olive. Both sexes share the species’ signature brilliant blue eyes.
Juveniles are difficult to sex until they begin to mature, typically around three to four months of age. When buying a group, aim for a mix — a ratio of roughly one male to two females reduces inter-male competition and encourages continuous display.
How do forktail blue-eyes breed?
Forktail blue-eyes are egg scatterers that deposit adhesive eggs among fine-leaved plants or spawning mops. Breeding difficulty is rated medium — adults spawn readily once well-conditioned, but raising fry is demanding because the newborns are tiny.
- Conditioning: Feed live or frozen baby brine shrimp and daphnia to both sexes for one to two weeks.
- Spawning site: Java moss, hornwort or wool spawning mops near the surface. Males display with spread fins and lateral shimmering.
- Eggs and incubation: Eggs are adhesive and deposited individually over several days; incubation is roughly ten to fourteen days at 24–26 °C (75–79 °F).
- Fry care: Fry are extremely small — start with infusoria or commercial fry powder before offering baby brine shrimp nauplii. Move mops to a separate rearing vessel for best survival.
- Adult management: Parents do not guard eggs and will eat them. Dense plant cover or daily mop removal improves yield.
What diseases should forktail blue-eye keepers watch for?
Common ailments affecting forktail blue-eyes are the same ones that affect small community fish generally:
- Ich (white spot disease): Small white spots resembling grains of salt on fins and body. Almost always triggered by a temperature drop or stress from shipping.
- Velvet (Oodinium): A fine gold or rust-coloured dust on the body, often first noticed under a torch. Highly contagious.
- Fin rot: Ragged or receding fin edges, typically a secondary consequence of poor water quality or physical damage from fin-nippers.
- Internal parasites: Occasional wasting or hollow-belly appearance, more common in wild-caught stock.
Prevention is straightforward: maintain excellent water quality, quarantine all new fish for two to four weeks before adding them to an established tank, and avoid sudden temperature swings. Because forktail blue-eyes are small, even a brief period of poor conditions can tip them toward illness quickly.
Health note: this profile covers prevention and recognition only. Medication selection, dosing and disease confirmation are beyond the scope of a care guide — consult a reputable veterinary or fish-health source before treating sick fish.
How long do forktail blue-eyes live?
With good care, forktail blue-eyes live 3–5 years — a solid lifespan for a nano fish. Achieving the upper end comes down to the fundamentals: stable, clean water, a varied diet, an adequate group size, and calm tank-mates. Because they are often sold as juveniles by specialist breeders rather than chain pet stores, you are more likely to get most of their lifespan ahead of you.
Frequently asked questions
Can forktail blue-eyes live in a nano tank?
Yes — their small adult size (under 5 cm) makes them one of the best choices for a planted 60-litre tank, provided you keep a school of at least six. They show their best colours and natural behaviour only in a group and with plenty of plant cover.
What do forktail blue-eyes eat?
They accept most small aquarium foods — micro-pellets, finely crushed flake, and frozen or live foods such as baby brine shrimp, daphnia and micro worms. Small-particle live and frozen foods are especially useful for conditioning breeding pairs and rearing fry.
What you need to keep a forktail blue-eye
The baseline is a heated, filtered 60 L+ tank: a reliable heater to hold 22–28 °C (72–82 °F), a gentle filter that won't batter a forktail blue-eye in the current, and a tight-fitting lid. Cycle the tank fully before adding any fish.
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