Encyclopaedia

FishFreshwaterEasy

Forktail Blue-eye

Pseudomugil furcatus

The Forktail Blue-eye (*Pseudomugil furcatus*) is a spark of pure aquatic joy. This micro-fish (maximum 5-6 cm / 2 inches) is characterized, as the name suggests, by bright neon blue eyes and a conspicuously forked caudal fin with sun-yellow edges. Males engage in continuous and exhausting dance displays, swimming in tight circles (sparring) and showing off their large upward-pointing pectoral fins. Their hyperactivity and dazzling color make them one of the most spectacular choices for heavily planted nano-aquariums.

Taxonomy

Class:Actinopteri

Order:Atheriniformes

Family:Pseudomugilidae

Genus:Pseudomugil

Species:Pseudomugil furcatus

Check out Forktail Blue-eye on Atlarium

PracticeRecognition quizzesPhotos, names, origins, and puzzles to review Atlas species.Open quizzes

Water Temperature

24 - 28 °C

pH Value

7 - 8

Water type

Freshwater

Tank level

Surface and middle

Adult size

6 cm

Minimum tank volume

>= 60 L

Minimum group

>= 8

5 - 15 dGH

2 - 7 dKH

TDS

95 - 295 ppm

Conductivity

148 - 461 uS/cm

Species description

Geographical Origin and Habitat: Papua New Guinea. Populates shaded forest rivers and streams with dense aquatic vegetation, clear water and moderate flow, often in limestone areas.

Taxonomy and Morphology: Forktail Blue-eye (Pseudomugil furcatus). Melanotaeniid. Characterized by two close dorsal fins (typical of blue-eyes). Penetrating iridescent blue eyes and forked tail (furcatus).

Social Behavior: Extremely gregarious and choreographic. Males swim shoulder to shoulder performing elaborate "Sparring dances", snapping their yellow fins up and down to intimidate each other and attract females, without ever getting hurt.

Coloration and Sexual Dimorphism: Spectacle in yellow. The body is semi-transparent golden. Males exhibit wide bright sunshine yellow margins on all fins and black stripes on the margins of the tail. Females are paler, with short, transparent fins.

Care, breeding and tankmates

Aquarium Setup: 80 cm (32 inches) tank. It is essential to provide ample space for open swimming and thick bushes of stem plants (Myriophyllum, Rotala) where males can establish temporary mini-territories and females can hide.

Diet and Feeding: Micro-insectivore. They have very small mouths and narrow throats. They only eat food floating in mid-water or on the surface. Live brine shrimp nauplii are the ideal food to trigger golden reflections.

Water Quality: Hard water lovers. Unlike Amazonian fish, they tolerate soft and acidic waters poorly. They require a pH between 7.0 and 8.0 and a medium-high GH to maintain perfect osmoregulation and avoid bacterial collapse.

Compatibility and Cohabitation: Peaceful community fish, perfect with other Rainbowfish, Corydoras and Loricariids. Not recommended to pair with aggressive fish, slow eaters (they would be outcompeted) or male Bettas (who would mistake their yellow fins for a threat).

Aquarium Breeding: Continuous scatterers. Females release a few adhesive eggs among the mosses every morning. Parents will eat their own eggs and larvae; to save the fry (which hatch in 15 days), use wool Mops and transfer them.

Risks and Diseases: Competition Exhaustion. Males in a group with few females will engage in challenges so grueling that they will end up losing weight, wearing out their fins and dying prematurely. Always maintain a ratio of 1 male to 2-3 females.

Geographic Origin and Distribution

Papua New Guinea. Populates shaded forest rivers and streams with dense aquatic vegetation, clear water and moderate flow, often in limestone areas.

Origin

Tropical oceans and reefsAfrica and MadagascarEast AsiaAustralia, New Guinea, and Oceania

Fish profile

Temperament: Active
Diet: Omnivore
Sex ratio: Specific M:F ratio
Feeding frequency: Twice daily
Bioload: The Forktail Blue-eye has a very low bioload. They are small fish that produce minimal waste. Regular maintenance is still required to keep the water pristine.
Flow: Moderate
Jump risk: Yes
Reproduction: Oviparous
Compatibility & tankmates: Verify
Tank level: Top/Middle

FishBase

Window to the official scientific data of the species

Data synced on: 06/15/2026

Scientific Parameters & Models

Trophic level: 3.3 ± 0.4 se
Phylogenetic uniqueness (PD50): 0.5
Bayesian Length-Weight: a = 0.01122, b = 3.04

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.

Related species

Recommendations grouped by close relatives, companion choices, and similar care.

Variants and close relatives

Same atlas type, nearby scientific identity, genus, or family.

Pacific Blue-eye

Pseudomugil signifer

Species description

Care, breeding and tankmates