Forktailed Rainbowfish Species Profile

Characteristics, Origin, and Helpful Information for Hobbyists

Small forktailed rainbowfish near bottom of fish tank with pebbles

The Spruce / Adrienne Legault

The forktailed rainbowfish, Pseudomugil furcatus, is easy to breed, beautifully colored and relatively hardy. Less than two inches when fully grown, this small rainbowfish fits in well with other small shoaling fish in a well-planted community aquarium. Providing that this fish is transferred over to its new aquarium home slowly, it will adapt to a wide range of water conditions ranging from soft and slightly acidic water to hard and alkaline.

Species Overview

Common Names: Forktailed rainbow fish, forktail blue eye

Scientific Name: Pseudomugil furcatus

Adult Size: 2 inches

Life Expectancy: 3 years


Family Pseudomugilidae
Origin New Guinea
Social Peaceful
Tank Level Middle
Minimum Tank Size 30 gallons
Diet Omnivore
Breeding Spawners
Care Easy
pH 7.0 to 8.0
Hardness 8 to 18  dGH
Temperature 75 to 79 F (24 to 26 C)

Origins and Distribution

Forktailed rainbowfish are native to Peria Creek and the Kwagira River of eastern Papua New Guinea; they exist in the wild in only a very small geographic area in Milne Bay Province. They occasionally travel into nearby rivers and tributaries, probably as a result of drainage among the different waterways.

These fish prefer slow-moving streams lined with heavy vegetation; these environments make it easy for them to find their favorite foods: zooplankton, phytoplankton, and invertebrates. Very few forktailed rainbowfish are collected in the wild. Because they are easy to breed, they are bred at fish farms for the aquarium trade.

Colors and Markings

The forktailed rainbowfish is a very attractive species with blue eyes, a silvery body, and bright yellow stripes on the top and bottom of the body in the breeding season. Two upturned almost wing-like pectoral fins, bright yellow in color along with bright yellow dorsal fins in breeding season make these little gems great additions to any community aquarium.


Forktailed rainbowfish are a shoaling species and should be kept with six to ten of their own kind. A generally peaceful fish, they can live comfortably with smaller goby or catfish species, danios, tetras, rasboras, dwarf cichlids, and other small rainbowfish. Do avoid keeping this species in a tank with slower-moving fish or fish with long, trailing fins as they do sometimes nip and can be a bit aggressive.

Forktailed Rainbowfish Habitat and Care

When creating a habitat for your forktailed rainbowfish, remember that their native environment is one of slow-moving water with a great deal of vegetation. To recreate a similar habitat, choose a 30-gallon or larger aquarium and add a dark, sandy or rocky substrate.

Decorate with river rocks, driftwoods, rooted plants, and floating feathery-leafed plants.  Floating plants over a dark substrate will not only bring out the colors in this species to the best effect, but the fish will be more comfortable and calm. Live plants are necessary for this fish to thrive. Be sure the water is well oxygenated. Use a large filtration system but one that doesn't create too much turbulence.

The forktailed rainbowfish is very active; it is not only fast but agile as well, swimming, twisting, and turning in and out of plants playfully. They are a middle zone fish and are in motion as long as aquarium lights are on. It is best to keep two males together with four to six females to induce the most active social displays. Forktailed rainbowfish need many hours to acclimatize to a new aquarium environment. Quick exposure to different water chemistry and temperature can shock their systems.

Forktailed Rainbowfish Diet and Feeding

A great advantage of the forktailed rainbowfish is their uncomplicated feeding requirement: they have almost no special needs. Choose flake, micropellets, and small frozen foods such as daphnia, baby brine shrimp (Artemia nauplii), and cyclops.

Gender Differences

Male forktailed rainbowfish can be distinguished by their sharper colors and a striking fin shape; fins are curved and almost wing-like and are bright yellow. Females and juveniles have the same basic coloring as males, but the colors are not as brilliant.

Breeding the Forktailed Rainbowfish

These fish are short-lived in nature so they mature quickly, and breed young. Males are prime at about eight months; after one year to 15 months, they will develop a pigeon chest, at which time they are too old or mature to breed. However, many forktailed rainbowfish do live to be very old fish in a community aquarium.

This species usually mates within the shoal and lays their eggs among feathery-leafed plants. Over the last 10 years, this remarkable member of the rainbowfish family has faded almost completely from the home aquarium scene. It is unfortunate, because not only is this remarkable fish one of the easiest of the rainbowfish to keep in a community aquarium, it is also one of the easiest of its kind to breed.

Using two males and six females, each male will set up his own “territory” in the well-planted breeding tank. One of the males will take possession of a fine-leaved plant or breeding mop at a far end of the tank. You will notice that the females will stay in the middle of the aquarium during this mating ritual; the other male may take possession of another plant of the breeding mop at the other end of the tank. 

You must get up at sunrise, or cause the lighting system in the breeding tank to simulate dawn, which is when the males will display for the females. This is worth getting up for as they become quite beautiful in their dances. Occasionally the males may have a brief skirmish for dominance, but they tend to ignore each other.

Eventually, a female will follow one of the males back to his chosen plant or breeding mop to spawn. You will know they are spawning when they dip to the lower reaches of the tank and swim up into the plant or mop close to each other. As they reach close to the top of the plant, they swim into each other and release eggs and milt together.

The most difficult part about breeding this remarkable fish is the wait for the eggs to hatch as it will take at least 14 days. Because of this delay, there is a real chance of losing the eggs to fungus if left in the breeding tank. Remove the eggs to a sterile water tank with fungus treatment to achieve the best results.

The fry (baby fish) of this species are unusual among the smaller egg-layers as they are free-swimming and self-sufficient at the time of hatching. They are immediately large enough to eat live baby brine shrimp and powdered dry food.

Use a sponge filter in the fry rearing tank after three weeks, change 20 percent of the water each week, and feed small amounts of varying foods six times a day. With luck and good attention to detail, at three months they will be over an inch long.

More Pet Fish Species and Further Research

If you’re interested in fish that might be good tankmates for your forktailed rainbowfish, check out:

Check out additional fish species profiles for more information on other freshwater fish.