Forktail blue-eye care guide

The forktail blue-eye (Pseudomugil furcatus) is one of the easiest and most colorful of the blue-eye rainbowfish. This guide covers what you need to keep a healthy, colorful group, based on the setup we use in our own fish room.

Quick facts

Tank size and setup

Forktails are small, but they swim constantly and need to be kept in groups. A 20-gallon long suits a group of 6–10 well. A 15-gallon works for a smaller group. Longer tanks beat taller ones because these fish use the upper and middle water column and need horizontal swimming room.

They look best in a planted tank with some open swimming space along the front. Fine-leaved plants and floating plants make them feel secure and give females somewhere to scatter eggs. Use a tight-fitting lid: like most rainbowfish, they can jump.

Gentle to moderate flow is ideal. A sponge filter or a hang-on-back filter with the flow turned down both work well.

Water parameters

Forktail blue-eyes prefer clean, well-oxygenated water that is neutral to slightly alkaline. Keep the temperature between 75 and 82 °F, the pH between 7.0 and 8.0, and the hardness moderate. Stability matters more than hitting an exact number, so avoid large, sudden swings.

Weekly water changes of 25–30% keep nitrates low and colors bright. Always add new fish to a fully cycled tank.

Diet and feeding

In the wild they eat small insects, larvae, and zooplankton. In the aquarium they readily accept:

• High-quality micro pellets and crushed flake
• Frozen baby brine shrimp, daphnia, and cyclops
• Live foods such as baby brine shrimp, daphnia, and microworms

Feed small amounts once or twice a day. Live and frozen foods bring out the strongest male color and condition fish for breeding. Their mouths are small, so choose foods sized accordingly. Our fish are raised on powdered fry food and live baby brine shrimp, so those are great foods to offer when they first arrive.

Tankmates

Forktails are peaceful and get along with other small, calm fish. Good companions include:

• Other small rainbowfish and blue-eyes
• Small tetras and rasboras
• Pygmy and dwarf corydoras
• Otocinclus
• Shrimp such as Neocaridina (adults are safe; baby shrimp may be eaten)

Avoid fin-nippers like tiger barbs and serpae tetras, and any fish big enough to swallow a 2-inch rainbowfish.

Males vs. females

Telling the sexes apart is easy in adult fish:

• Males have brighter yellow fins, extended rays on the dorsal and anal fins, and a more pronounced forked tail. They spend much of the day sparring and displaying to each other.
• Females are plainer, with clearer or paler yellow fins and a rounder belly.

Keep at least as many females as males, and ideally more (for example 1 male to 2 females). That spreads out the males' attention and keeps the group calm.

Acclimating new fish

When your fish arrive, float the sealed bag for about 15 minutes to match temperature. Then add small amounts of tank water to the bag over 20–30 minutes before netting the fish into the tank. Don't pour shipping water into your aquarium. Keep the lights dim for the rest of the day.

Common questions

How many forktail blue-eyes should I keep together?

At least six. They're a schooling species, and males display their best colors when they have rivals and females around.

Are forktail blue-eyes good for beginners?

Yes, as long as the tank is cycled and the water is clean and stable. Captive-bred fish are much hardier than wild-caught ones.

Can forktail blue-eyes live in a nano tank?

A small group can live in a 10-gallon, but they're happier and show better behavior in 15–20 gallons or more.

Is Popondetta furcata the same fish?

Yes. Popondetta furcata and Popondichthys furcatus are older names for the same species, now classified as Pseudomugil furcatus.

Ready to start a group? See our current availability →
Interested in raising fry? Read our breeding guide →