Product Details

Boeseman’s Rainbowfish – Melanotaenia boesemani “Lake Ajamaru”

The Boeseman’s Rainbowfish is one of the most recognisable rainbowfish in the aquarium hobby, famous for the mature male’s blue front half and yellow-orange rear half. This Lake Ajamaru form of Melanotaenia boesemani represents an important West Papuan locality strain and is best kept in spacious, mature aquariums with clean water, open swimming room and a proper group. It is peaceful with suitable tank mates, but active and fast-moving, so it is better suited to confident community fish than shy nano species.

Key Identification:

Common Name: Boeseman’s Rainbowfish
Other Names: Boesemani Rainbowfish, Boeseman’s Rainbow, Lake Ajamaru Rainbowfish, Ajamaru Boesemani
Scientific Name: Melanotaenia boesemani “Lake Ajamaru”
Fish Type: Rainbowfish / Melanotaeniid
Water Type: Freshwater

Natural Range & Habitat:

Melanotaenia boesemani is native to West Papua, Indonesia, where it is strongly associated with the Ajamaru Lakes region on the Vogelkop Peninsula. It has also been recorded from nearby Aitinjo Lake. The Lake Ajamaru form should be treated as a locality strain and maintained carefully by aquarists interested in preserving line identity.

In the wild, Boeseman’s Rainbowfish are associated with lake systems, connecting creeks and vegetated freshwater margins. In the aquarium, they should be kept in a mature, well-filtered setup with open midwater swimming space, planted edges, moderate flow and good oxygenation.

Appearance & Adult Size:

Boeseman’s Rainbowfish are deep-bodied, laterally compressed rainbowfish with a distinctive two-tone colour pattern. Mature males usually show a blue, bluish-grey or purple-blue front half with a yellow, orange or golden rear half. Females and juveniles are generally slimmer and more subdued, often appearing silvery, olive or pale yellow until mature.

Adults usually reach around 8–10 cm, with males typically larger and deeper-bodied than females. The strongest colour is usually seen in mature males kept in a settled mixed-sex group with good diet, clean water and plenty of swimming space.

Aquarium Suitability:

This species is best suited to larger peaceful community aquariums, planted rainbowfish displays and active New Guinea-style setups. It suits aquariums with open swimming lanes, plants around the sides and back, and enough room for males to display.

Boeseman’s Rainbowfish are not suitable for tiny aquariums, shy nano communities, aggressive cichlid tanks, predator aquariums or cramped layouts with little swimming room. They are peaceful, but their constant movement can intimidate very small or timid fish.

Recommended Aquarium Size:

A practical minimum is 180 litres for a group, with a tank length of at least 100 cm recommended. Larger aquariums of 240 litres or more are preferred for mature groups, mixed rainbowfish displays and better long-term colour development.

Keep in a group of at least 6, with 8 or more preferred. A mixed-sex group is ideal, as males show stronger colour and display behaviour when females and rival males are present.

Water Conditions:

Temperature: 24–28°C
pH: 7.0–8.0
Hardness: Moderately hard to hard preferred
Additional Notes: Keep water clean, stable and well oxygenated. This species appreciates regular partial water changes, strong biological filtration and steady mineral content. Avoid poor oxygenation, high nitrate, sudden water-chemistry changes and cramped, stagnant aquariums.

Temperament & Tank Mates:

Aquarium Category: Community Fish

Boeseman’s Rainbowfish are peaceful but active community fish. Suitable tank mates include other rainbowfish of similar size, larger peaceful tetras, danios, robust rasboras, peaceful barbs, Cory-type catfish in compatible temperatures, bristlenose plecs and other confident community species.

Avoid very small nano fish, shy slow feeders, long-finned delicate species, large predators and aggressive cichlids. Adult rainbowfish may eat very small fry or tiny shrimp, so they are not ideal for shrimp-breeding aquariums.

Feeding:

Boeseman’s Rainbowfish are easy-feeding omnivores. Offer quality flakes, small floating or slow-sinking granules and rainbowfish pellets as the staple diet. Supplement with frozen or live foods such as daphnia, cyclops, brineshrimp, mosquito larvae, bloodworm and small insect-based foods.

A varied diet supports colour, body condition and display behaviour. Feed small amounts that are eaten quickly, as active rainbowfish have strong appetites and do best with clean water.

Behaviour in the Aquarium:

This is an active midwater swimmer that spends much of the day moving through open areas of the aquarium. Males may display to females and rival males by intensifying colour, flaring fins and making short chasing movements. This is normal in a suitable group and usually does not cause harm when there is enough space.

Boeseman’s Rainbowfish are egg scatterers. Females deposit adhesive eggs among fine plants, mosses or spawning mops, and adults do not provide parental care. Fry require separate rearing if breeding is intended.

Care Notes:

Add Boeseman’s Rainbowfish only to a mature, fully cycled aquarium. Provide open swimming room, stable water quality and a secure lid, as active rainbowfish can jump when startled. Avoid overcrowding, poor oxygenation and long periods without water changes.

Do not mix Lake Ajamaru fish with other Melanotaenia boesemani locality strains if breeding for line purity. This is especially important with conservation-sensitive rainbowfish, where responsible captive breeding helps preserve clear, traceable aquarium lines.

Recommended For:

Intermediate

Availability:

Common to occasional / Usually captive-bred, with locality strains less common

Image Disclaimer:

All images are a visual representation of the fish you will receive, made to be as accurate as possible. Natural variation in size, blue colour, orange colour, metallic sheen, fin length, sex, age and markings can occur between individual fish.