Forktail Blue-eye Rainbowfish

Pseudomugil furcatus is one of the most striking blue-eyes available in the hobby, the deeply forked caudal fin giving males a distinctly elegant silhouette. The body is pale silver-yellow, and the fins — particularly the dorsal, anal, and caudal — are richly patterned with vivid yellow and black markings that flash brilliantly during courtship. Despite measuring only about 5 cm at maturity, this is one of the most visually impactful nano fish in freshwater aquaristics.

Originating from the Kwagira River (also known as the Gira River) near Popondetta in Papua New Guinea, it inhabits shallow, clear, well-oxygenated streams. In the aquarium it does best in slightly alkaline, moderately hard water with good current and abundant plant cover — particularly fine-leaved stem plants and floating plants that diffuse light and provide spawning sites. Males display constantly and the activity is mesmerising.

Pseudomugil furcatus breeds readily in captivity and deposits small adhesive eggs on fine vegetation or spawning mops. The fry are very small and require infusoria or commercial fry food before graduating to baby brine shrimp. It is one of the more popular blue-eye species and is available from specialist suppliers.

Water: pH 7.0–8.0, temperature 22–28°C, moderately hard; clean, well-oxygenated water essential. Tank: Minimum 40 L; heavily planted with fine-leaved plants and floating cover; gentle to moderate flow. Feeding: Micro-pellets and fine flake; baby brine shrimp, micro-worms, and daphnia nauplii several times weekly. Breeding: Deposits eggs on fine plants or mops; fry require infusoria initially; easily bred in species tank. Compatibility: Peaceful nano species; excellent with small rasboras, micro-tetras, and dwarf shrimp.