Forktail Blue-eye Rainbowfish (Pseudomugil furcatus)

The Forktail Blue-eye (Pseudomugil furcatus) is one of the most visually striking members of the Pseudomugilidae family, native to clear, fast-flowing hill streams and rivers of Papua New Guinea's Sepik River drainage. Its common name refers to the distinctive forked caudal fin of males, whose upper and lower lobes are elongated and edged with vivid yellow-orange, creating a dramatic W-shaped tail profile.

Males are spectacularly colored: the body is semi-transparent with a golden dorsal surface, brilliant blue irises (the defining 'blue-eye' characteristic shared across the genus), and the stunning forked tail with yellow-tipped extensions. The dorsal and anal fins are also edged with yellow and may show dark leading edges. Females are smaller, less colorful, and lack the elaborate fin extensions.

In their natural habitat, Forktail Blue-eyes inhabit fast-flowing, clear, well-oxygenated streams with gravel and rocky substrates, aquatic vegetation, and overhanging riparian vegetation. Water tends to be cool-to-warm, slightly acidic to neutral, and soft to moderately hard.

In the aquarium, males engage in constant courtship displays — erecting fins, spreading their spectacular tails, and performing elaborate swimming patterns to attract females. When multiple males are present in a group, this display behavior intensifies, creating a truly mesmerizing spectacle. They are peaceful, active fish perfectly suited to planted nano and small aquariums.

Forktail Blue-eyes prefer clean, well-oxygenated, slightly acidic to neutral water: pH 6.5–7.5, hardness 5–12 dGH, and temperatures 22–28°C. They are sensitive to poor water quality and do best with pristine conditions maintained through excellent filtration and regular water changes.

A minimum 60-liter aquarium with gentle to moderate current suits a group well. Dense plantings of fine-leaved plants (Java moss, Hornwort, Ceratophyllum) and floating plants provide spawning sites — they scatter eggs among fine vegetation. Gentle sponge filtration or spray bars distribute current without creating excessive flow.

Feed small, varied foods: micro pellets, baby brine shrimp, daphnia, micro worms, and crushed flake. Their small mouths require appropriately sized food particles. Feed 2–3 times daily in small amounts.

Forktail Blue-eyes are peaceful and suitable with other small, gentle species: nano rasboras, small corydoras, small shrimp, and other Pseudomugil species. Avoid boisterous or nippy fish that may damage their delicate fins or outcompete them for food.

Maintain groups with more females than males (2:1 female ratio) to distribute male courtship pressure. Keep in groups of at least 6 for natural behavior. Regular small water changes (20–25% twice weekly) maintain the water quality this sensitive species requires.