Forktail Blue Eye (Pseudomugil furcatus)

Common Name

Forktail Rainbow, Forktail Blue Eye, and Furcata Rainbowfish. You may also see this fish sold under the older name Popondetta furcata, but the accepted scientific name is Pseudomugil furcatus.

Origin and Habitat

Forktail Rainbows come from the lowlands of eastern Papua New Guinea, where they live in small rainforest streams and quiet margins with clear water and heavy aquatic plant growth. They tend to stay in the upper half of the water column, moving in loose groups through vegetation and open lanes.

Biotope and Natural Setup

If you want a location inspired setup, think Papua rainforest creek, clear water, green everywhere, rounded stones and cobble, branchy wood, and dense plants along the edges with open swimming space through the middle. Keep the current gentle to moderate, with high oxygen and strong filtration, but avoid turbulent blasting flow. A tight fitting lid is strongly recommended.

Biotope accurate fish species, based on documented co occurrence in nature

• Forktail Rainbow, Pseudomugil furcatus
• Peacock Gudgeon, Tateurndina ocellicauda

Papua New Guinea inspired companion fish that match the region well

Note: they may not come from the exact same creek

• Spotted Blue Eye, Pseudomugil gertrudae
• Popondetta Blue Eye, Pseudomugil connieae
• Threadfin Rainbowfish, Iriatherina werneri

Biotope accurate or region appropriate plant picks

• Aponogeton womersleyi
• Vallisneria nana
• Ceratopteris thalictroides (water sprite)
• Hydrilla verticillata

Temperature and Water Conditions

A dependable everyday target is 24 to 27°C (75 to 80°F), with clean, well oxygenated water and stable parameters. Many keepers have the best results in neutral to slightly alkaline water, with moderate hardness. We do not recommend chasing exact numbers unless you are dialing things in for breeding. Stability and water quality matter more than perfection.

Appearance and Size

This is one of the best looking small schooling fish for planted aquariums. The eyes shine electric blue when the light hits, and the fins show bright yellow accents with a crisp forked tail pattern. Adults are usually about 5 cm (2.0 inches), with females typically a bit smaller and males showing stronger color and longer finnage.

Diet in the Wild

Forktail Rainbows pick at tiny foods in the water column and among plants, including small insects and larvae, micro crustaceans, and other plankton sized prey.

Feeding in Captivity

Feed small foods they can actually fit, and keep variety in the rotation. A quality micro pellet or fine flake works as a base, then rotate in frozen or live foods like baby brine shrimp, daphnia, cyclops, and other micro foods. They are quick at feeding, so watch slower tankmates to make sure everyone gets a share.

Behavior and Tank Setup

Forktail Rainbows are peaceful, social, and very active. They look best in a proper group, and they behave more confidently as the group size increases. A longer footprint helps them show their natural cruising and display behavior. They are energetic enough to jump, so a lid is not optional if you want to sleep well.

If you keep both sexes, males will posture and display in a looping dance. It is more show than fight, and it is part of the fun of keeping them.

Breeding

They are enthusiastic spawners when conditioned well. Eggs are deposited into fine plants or spawning mops, and only a small number of eggs are typically produced each day rather than one huge spawn. Incubation is commonly reported around 15 to 20 days at about 25 to 28°C (77 to 82°F). With good food and stable water, young fish can be ready to spawn at roughly 3 to 4 months of age.

Breeder’s Tips

• Use a yarn spawning mop or fine leaf plants, placed where gentle flow moves it slightly
• Condition breeders with frequent small meals, including live baby brine shrimp or other rich micro foods
• Check spawning media regularly and move eggs to a small hatching container with clean water and gentle aeration
• Start fry on infusoria or other microscopic foods, then baby brine shrimp as soon as they can take it
• Do small, frequent water changes for steady growth and clean water without swings

Quick Facts

• Scientific name: Pseudomugil furcatus
• Adult size: about 5 cm (2.0 inches)
• Recommended temperature: 24 to 27°C (75 to 80°F)
• Social behavior: schooling, keep in groups (8 to 10 is a great starting point)
• Tank size: a 20 gallon or larger footprint is strongly recommended for their activity level
• Jump risk: yes, use a lid
• Breeding: egg scatterer, eggs often hatch in about 15 to 20 days at 25 to 28°C (77 to 82°F)
• Lifespan: reports suggest around 4 years in the wild and up to about 8 years in captivity with good care

Tropical Fish Co. Notes

Forktail Rainbows are one of the easiest ways to make a planted aquarium feel alive. They are small, but they never feel like background fish. Those electric blue eyes catch the light like tiny LEDs, the yellow fins glow against green plants, and the forked tail pattern makes the whole group look sharp and intentional, like they are all wearing matching uniforms.

What really sells this species is the movement. In a good sized group they are constantly weaving through stems, lining up, breaking formation, then snapping back together like a school of little arrows. Males will posture and do their looping display dances, not aggressive, just dramatic, and it turns the top half of the tank into a nonstop show.