Forktail Blue-eye

1 Species Overview

The forktail blue-eye is a small rainbowfish with a pale blue-green, semi-transparent body that looks beautiful swimming in the aquarium, so it costs more than other rainbowfish.

Latin name: Pseudomugil furcatus

Kingdom: Animalia

Chinese name: Forktail blue-eye

Family: Pseudomugilidae (blue-eye family)

Habits: Schooling in mid and upper water

Origin: New Guinea, Australia

Staple food: Live animal foods

Also known as: Rainbow Fish

Water (pH): 6.5 to 7.5

2 Appearance and Physical Traits

The forktail blue-eye has a very special color and a small, delicate body; adults are only about two inches (6 cm) long, so it does not need a large tank—a common round glass goldfish bowl will do.

Both sexes share a yellow-green base color, but males show a bright beautiful yellow on the lower belly. The dorsal and anal fins are transparent with a narrow yellow edge. The pectoral and pelvic fins are usually slightly orange-red. The caudal fin is somewhat dark with a clear wide yellow upper and lower edge and a narrower black edge. The forktail blue-eye is small and delicate, only two inches (6 cm) as an adult, so a traditional round glass goldfish bowl is enough. A larger planted tank with sand and rock shows off its black-and-bright-yellow form even better.

The forktail blue-eye matures in about 5 months; males show bright yellow on the lower belly, and the dorsal, caudal, and other fins are vivid yellow or orange-yellow, while the top and bottom edges of the dorsal fin carry a black border. Females look much like males but are less vivid yellow and rather dull.

3 Habitat and Living Environment

The forktail blue-eye is not hard to keep, but ignoring its environment easily leads to disease. Its gentle temperament makes it suit mixing with other small, equally gentle tropical fish.

The forktail blue-eye has a fairly long aquarium history; it was kept in pet circles worldwide on a small scale as early as fifteen years ago. Its strength is that it likes alkaline hard water—tap water in northern China can be used directly for breeding.

Note that the forktail blue-eye is very prone to velvet disease, its biggest weakness. Velvet is a common protozoan (some class it as algae) causing bacterial skin infection. Pale fish hide the symptoms, and the disease rarely threatens larger goldfish, but for the forktail blue-eye it is fatal. This is why some keepers find their fish mysteriously dull and sluggish.

The cause is mainly owners forgetting regular water changes, raising ammonia and waste levels that stress the fish into illness. So it is easy to prevent: change water often in the right amount and keep good surface filtration. Remember to clean and replace filter media often. Because this fish needs no special water treatment—tap water is fine—water changes are easy.

4 Feeding Guidelines

Keeping the forktail blue-eye means watching water and also feeding scientifically; without it, food pollutes the tank.

Adults eat live animal foods; fry start on vinegar eels and microworms, then after two or three days take newly hatched brine shrimp. Some say the fry are hard to raise, but the blue-eye fry’s advantage shows early: they grow much faster than rainbowfish fry. With good food and frequent water changes, they reach a vivid two-inch adult in three or four months.