Melanotaenia boesemani

Common Names: Bicolor rainbow, boes, Boeseman’s/Boesman’s rainbowfish, boesemani, etc.

Type Locality: N/A

Range: Indonesia: Irian Jaya, lakes at the headwaters of the Ajamaru River

Taxonomic Troubles: This is the original description.

Size: About 10 cm (4 inches), females smaller than males.

Preferred Water Chemistry: Tropical freshwater. Looks its best in warm, hard, neutral to basic water.

Difficulty: Moderate. The major factor that makes this fish suitable only for hobbyists with some experience is that they are extremely active fish that must be kept in schools, therefore requiring rather large aquaria—at least 4 feet long.

Tank Setup: Perfect fish for a large community setup. A planted tank is fine, but keep the front area uncluttered for swimming room. Very often fish more than 3 or 4 inches long present problems for a community setup, but rainbowfish are peaceful and well behaved, an

Feeding: Omnivorous. Will take all foods, dry, freeze-dried, frozen, and live. They especially love live worms and mosquito larvae and should also have some vegetable foods.

Breeding: While males may display to females at any time, true spawning behavior takes place at dawn, with eggs deposited in plants or mops. Some fry may survive if there is sufficient cover, but for maximum success, the eggs should be moved to a separate aquarium.

Fish Description

A bicolor pattern reminiscent of some marine fishes, blue-gray on the front half and orange-yellow on the back half. As males mature they develop intense coloration and the arched, high body to which some attribute the name “rainbow”; females and juveniles are slender and have paler colors.


Since its introduction to the hobby, this rainbowfish has remained very popular. Fish that are half one color and half another are always sought after, but most such species are marine. Boeseman’s rainbow is one of the few freshwater choices. There is considerable variation in the color of various domesticated strains (and probably of wild populations as well), with some sporting intense blue-orange patterns while other have faded gray-yellow coloration. Do not make the mistake of acquiring just one or a pair. Not only will the fish languish, you will miss out on their natural beauty and behavior. Like all rainbowfish, they make a spectacular display when kept in schools of at least six in a large planted tank. If a bit of morning sun hits the tank, you can witness their spectacular morning displays much as nature intended. They are active and beautiful all day, but the daily lights-on show is magnificent.