Product Details

Boeseman’s Rainbowfish – Melanotaenia boesemani “Lake Ajamaru”

Overview:

The Boeseman’s Rainbowfish “Lake Ajamaru” is one of the most iconic New Guinea rainbowfish, famous for mature males that show a blue to purplish front half and a warm yellow-orange rear half. This Lake Ajamaru locality form of Melanotaenia boesemani is a peaceful, active shoaling fish for a spacious planted aquarium with clean, mineral-rich water. Small fish may arrive looking fairly plain, but with maturity, good diet and a proper group, males develop the bold colour contrast that makes this species so popular.

Key Identification:

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

Natural Range & Habitat:

The Lake Ajamaru form is associated with the Ajamaru Lakes region on the Vogelkop Peninsula of West Papua, Indonesia. FishBase lists Melanotaenia boesemani as known from the Ajamaru Lakes region, with additional occurrence in nearby Aitinjo Lake. It also notes that the species inhabits lakes at the headwaters of the Ajamaru River system, which eventually drains towards the Ceram Sea.

In nature, Boeseman’s Rainbowfish occur in lake and creek habitats with clear freshwater, vegetation and open swimming areas. Animal Diversity Web notes that the species is indigenous to the Ajamaru Lakes region and Aitinjo Lake, and that it has been recorded in small creeks leading into Ajamaru Lake.

Appearance & Adult Size:

Young Boeseman’s Rainbowfish are often silver-grey with only hints of adult colour, so small specimens should not be judged too early. Mature males develop the classic bicolour pattern, usually with a blue, grey-blue or purplish front half and a yellow, orange or orange-red rear half. Females are typically slimmer and less intensely coloured, but they are important for natural group behaviour and male display.

Adults usually reach around 10–12 cm, with males becoming noticeably deeper-bodied as they mature. FishBase gives an aquarium profile for M. boesemani and places it among medium-sized, active rainbowfish rather than small nano species.

Aquarium Suitability:

This is an excellent fish for a larger planted community aquarium, New Guinea-style display or mixed rainbowfish setup. It needs open swimming room through the middle and upper levels, with plants, wood or décor around the sides and back for security. Boeseman’s Rainbowfish are peaceful, but they are fast and energetic, so they are not ideal for tiny tanks, shy nano fish or slow delicate species that may be unsettled at feeding time.

Recommended Aquarium Size:

A practical minimum is 240 litres for a group, with a tank length of at least 120 cm recommended. Larger aquariums are preferred for adult males, stronger display behaviour and mixed rainbowfish communities. FishBase notes aquarium keeping in groups of five or more, with an 80 cm minimum aquarium size, but a longer and larger tank is more appropriate for adult groups.

Water Conditions:

Temperature: 25–29°C
pH: 7.0–8.0
Hardness: Moderately hard to hard preferred
Additional Notes: Provide clean, well-filtered and well-oxygenated water with regular partial water changes. FishBase lists M. boesemani at pH 7.0–8.0, hardness 9–19 dH and tropical temperatures around 27–30°C. Seriously Fish also notes that this species is not suited to soft, acidic conditions long term.

Temperament & Tank Mates:

Aquarium Category: Community Fish

Boeseman’s Rainbowfish are peaceful but active shoaling fish. Suitable tank mates include other rainbowfish, larger tetras, danios, peaceful barbs, robust rasboras, Cory-type catfish that tolerate similar water, bristlenose plecs, peaceful loaches and calm medium-sized cichlids.

Avoid aggressive cichlids, persistent fin-nippers, very tiny fish and slow, timid species that may be intimidated by fast feeding. Keep in a group of at least 6, with 8 or more preferred. A mixed-sex group is best, as males usually colour up most strongly when displaying to females and rival males.

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, brineshrimp, cyclops, mosquito larvae and bloodworm. Include vegetable or algae-based foods for balance. Feed measured portions, as rainbowfish are enthusiastic feeders and can outcompete quieter fish.

Behaviour in the Aquarium:

This species spends much of its time in the middle and upper levels, moving in a loose group. Males display with raised fins, stronger colour and quick side-by-side movements, especially in the morning or after water changes. They are lively rather than aggressive, and a well-sized group usually shows better colour, confidence and natural behaviour than a small number of fish.

Care Notes:

Buy small specimens with their adult size in mind. They need a long tank, a group, stable mineral-rich water and good filtration. Do not keep singly or in pairs, as small numbers can become nervous and less colourful. Use a secure lid, as active rainbowfish may jump when startled. Locality forms such as Lake Ajamaru should not be mixed with other Melanotaenia boesemani lines if breeding may occur, as this can lose the locality identity.

Recommended For:

Beginner to intermediate

Availability:

Common to occasional / Captive-bred locality strain

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, colour, pattern and markings can occur between individual fish.