Ajamaru Rainbowfish
Melanotaenia ajamaruensis
A highly active, schooling rainbowfish endemic to the Ayamaru Lakes in West Papua, Indonesia. Currently listed as Critically Endangered in the wild. It is closely related to Boeseman's Rainbowfish but possesses a notably more slender body and more prominent reddish-brown horizontal striping. They thrive in hard, alkaline water with dense vegetation and require significant horizontal swimming space.
Ajamaru Rainbowfish At a Glance
Ajamaru Rainbowfish Tank Requirements
Will Ajamaru Rainbowfish fit in your tank?
Care guides tell you what Ajamaru Rainbowfish needs, the next question is whether your tank can safely provide it. Test Ajamaru Rainbowfish against your tank size, maintenance needs, and the fish you already keep before you buy.
Ajamaru Rainbowfish Water Parameters
Ajamaru Rainbowfish Temperament & Compatibility
Ajamaru Rainbowfish Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Male
Males display striking coloration (often metallic blue, yellowish, or green base with prominent reddish-brown horizontal stripes) and develop a slightly deeper body and longer finnage as they mature. They will actively display to each other and females.
Differs in 1 trait from base species
Also known as: Show Male, Standard
Female
Females are slightly smaller, more streamlined, and exhibit subdued, silvery-brown or mauve coloration. It is highly recommended to keep a ratio of 2-3 females per male to disperse the males' active breeding pursuit.
Differs in 1 trait from base species
Also known as: Unsexed, Juvenile
Ajamaru Rainbowfish Care Guide Summary
The Ajamaru Rainbowfish, scientifically known as Melanotaenia ajamaruensis, belongs to the Rainbowfish family group. Adults reach a maximum size of approximately 11 cm and have a compressed body shape with a moderate growth rate. Classified as peaceful, this species primarily occupies the surface and mid-level zones of the aquarium and produces a low level of biological waste.
To thrive, the Ajamaru Rainbowfish requires a freshwater only aquarium with a minimum volume of 150 litres and a tank length of at least 90 cm. Water temperature should be maintained between 24°C and 28°C, with a pH range of 7.2–8.5 and a general hardness of 8–20 dGH. A moderate water flow is preferred.
The Ajamaru Rainbowfish is a rewarding species to keep, provided its core environmental needs are met. This species is available in 2 varieties: Male and Female. Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
Ajamaru Rainbowfish Habitat Setup
When setting up an aquarium for the Ajamaru Rainbowfish, a moderate water flow best suits their natural preferences. Because this species occupies the surface and mid-level zones, the aquarium layout should prioritise adequate surface area with floating cover to make them feel secure near the waterline and open swimming space in the centre of the tank for free movement. Useful additions include dense planting to provide cover, break sightlines, and reduce stress. Keepers should note that a tight-fitting lid is essential, as this species is a known jumper.
Ajamaru Rainbowfish Compatibility Notes
Classified as peaceful, the Ajamaru Rainbowfish is a schooling species that feels most secure in a sizeable group, where natural shoaling behaviour reduces stress and brings out their best colours. When choosing tankmates, their energetic swimming style may stress more sedentary or timid species. Selecting tankmates that favour different water layers from the surface and mid-level zones can help reduce competition and territorial overlap.
Who Ajamaru Rainbowfish Is Actually For
Ajamaru Rainbowfish is best for a fishkeeper who wants a species that can settle into a calmer community setup and can provide a keeper who can commit to a proper group of at least 6. It makes the most sense for a hobbyist who will actually build around its needs, especially plants.
The most common mistake is buying Ajamaru Rainbowfish for looks first and only later discovering how its adult size, behavior, or bioload changes the whole tank plan. Another frequent problem is underestimating its social needs. A token pair or trio often behaves very differently from a real group.
Ajamaru Rainbowfish Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Ajamaru Rainbowfish.
40 Gallon Breeder
55 Gallon Standard
60 Gallon Breeder
75 Gallon Standard
90 Gallon Standard
125 Gallon Standard
Show 9 more tank sizes
Frequently Asked Questions About Ajamaru Rainbowfish
How big does Ajamaru Rainbowfish get?
Ajamaru Rainbowfish (Melanotaenia ajamaruensis) typically reaches a maximum adult size of approximately 11 cm. They have a compressed body shape and a moderate growth rate.
What tank size does Ajamaru Rainbowfish need?
A minimum aquarium volume of 150 litres and a tank length of at least 90 cm are recommended for Ajamaru Rainbowfish. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Ajamaru Rainbowfish need?
Ajamaru Rainbowfish thrives in freshwater only conditions with a temperature range of 24–28°C, a pH between 7.2 and 8.5, and a general hardness of 8–20 dGH. A moderate water flow is preferred.
Is Ajamaru Rainbowfish peaceful or aggressive?
Ajamaru Rainbowfish is classified as peaceful with an aggression score of 2 out of 10. They are generally well-suited to peaceful community tanks.
How many Ajamaru Rainbowfish should be kept together?
Ajamaru Rainbowfish is a schooling species and should be kept in groups of at least 6. Larger groups help distribute aggression and encourage natural schooling behaviour.
Does Ajamaru Rainbowfish have any special tank requirements?
Yes. Ajamaru Rainbowfish benefits from plants - densely covered in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Does Ajamaru Rainbowfish need a lid on the tank?
Yes. Ajamaru Rainbowfish is a known jumper, and a tight-fitting lid or cover is essential to prevent escape. Even a small gap can be enough for a determined fish to leap out.
Useful setup supplies
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Guidarium Editorial Desk
Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.
- Last reviewed
- May 2, 2026
- Last updated
- May 2, 2026
- Issues or corrections?
- Contact the editorial team
Top Tank Mates for Ajamaru Rainbowfish
These fish are strong compatibility matches for Ajamaru Rainbowfish based on water preferences, temperament, adult size, and tank behavior.
Trapdoor Snail
Cipangopaludina chinensis
Ideal Tank MatesXenotilapia ochrogenys
Xenotilapia ochrogenys
Ideal Tank MatesTandanus Catfish
Tandanus tandanus
Ideal Tank MatesPetricola Catfish
Synodontis petricola
Ideal Tank MatesEmerald Green Cory
Corydoras splendens
Ideal Tank MatesAgassiz Cory
Corydoras agassizii
Ideal Tank MatesPlants That Suit Ajamaru Rainbowfish
These plants pair well with Ajamaru Rainbowfish based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
Afzel's Anubias
Anubias afzelii
Amazon Sword
Echinodorus amazonicus
Anacharis
Egeria densa
Anubias Barteri
Anubias barteri
Baby Tears
Lindernia rotundifolia
Balansae
Cryptocoryne crispatula
Fish Similar to Ajamaru Rainbowfish
Boeseman's Rainbowfish
Melanotaenia boesemani
An incredibly popular and active schooling fish endemic to the Ajamaru Lakes in West Papua, Indonesia (currently listed as Endangered in the wild by the IUCN due to overfishing and habitat loss, though commercially captive-bred). Famous for the mature male's spectacular blue and orange split-coloration. They require long tanks for active swimming, excellent oxygenation, and warm, hard, alkaline water to thrive.
Lake Wanam Rainbowfish
Glossolepis wanamensis
A critically endangered species (IUCN Red List) endemic to Lake Wanam in Papua New Guinea. Known for the extreme deep-bodied shape and metallic green-bronze colors that mature males develop. They are fast, active schooling fish that require hard, alkaline water and plenty of swimming space. Excellent for large planted aquariums.
Lake Mbuta Rainbowfish
Pelangia mbutaensis
A very rare and Critically Endangered rainbowfish endemic to the swampy Lake Mbuta basin in West Papua, Indonesia. It is the sole member of the genus Pelangia. Characterized by a yellowish-tan body grading to silvery-white, they are peaceful, active schooling fish. They are virtually unseen in the standard aquarium trade.
Sentani Rainbowfish
Chilatherina sentaniensis
A critically endangered and highly active shoaling fish endemic to Lake Sentani in Papua, Indonesia. Known for their energetic, almost chaotic swimming patterns and ravenous feeding habits. While rarely seen in the general trade, they are highly prized; males develop spectacular blood-red to pinkish hues and arched backs as they mature. Requires a large aquarium with significant open swimming space and clean, oxygen-rich water.
Waigeo Rainbowfish
Melanotaenia catherinae
A rare but beautiful schooling fish endemic to the streams and springs of Waigeo Island in West Papua, Indonesia. They are highly active, energetic mid-water swimmers. Like most rainbowfishes, they are peaceful and thrive in planted community tanks that still offer plenty of open swimming space. They display a distinctive, unusually wide mid-lateral stripe and reddish fins.
Grime Rainbowfish
Glossolepis dorityi
A rare and highly active schooling fish native to the Grime River system in New Guinea, currently listed as Critically Endangered in the wild. Widely known in the hobby as Dority's Rainbowfish, they are prized for the male's unique zigzag lateral striping. They are peaceful community fish that require spacious, well-oxygenated tanks with plenty of open swimming room.