New Guinea Rainbowfish
Melanotaenia affinis
An active, schooling species native to the streams of northern New Guinea. Known for their striking lateral stripe and vibrant fin coloration that flashes during morning displays. They are peaceful but highly energetic, requiring ample open swimming space and highly oxygenated water to thrive.
New Guinea Rainbowfish At a Glance
New Guinea Rainbowfish Tank Requirements
Will New Guinea Rainbowfish fit in your tank?
Care guides tell you what New Guinea Rainbowfish needs, the next question is whether your tank can safely provide it. Test New Guinea Rainbowfish against your tank size, maintenance needs, and the fish you already keep before you buy.
New Guinea Rainbowfish Water Parameters
New Guinea Rainbowfish Temperament & Compatibility
New Guinea Rainbowfish Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Standard / Unsexed
Typically sold in stores as juveniles. They appear somewhat dull and slender but will undergo a dramatic transformation, developing deep bodies and rich colors as they mature in a well-maintained school.
Same care requirements as the base species
Also known as: Juvenile
Male
Adult males develop a significantly deeper, arched back and display brilliant coloration, especially on the edges of their fins. They frequently 'flash' their colors to establish hierarchy and attract females.
Differs in 2 traits from base species
Also known as: Show Male
Female
Females remain more slender and exhibit more subdued, silver or olive/yellow coloration. A proper ratio of females (often 1:1 or 2:1 female to male) is essential to diffuse male attention and encourage natural spawning displays.
Differs in 1 trait from base species
Also known as: Female
New Guinea Rainbowfish Care Guide Summary
The New Guinea Rainbowfish, scientifically known as Melanotaenia affinis, belongs to the Rainbowfish family group. Adults reach a maximum size of approximately 11.5 cm and have a compressed body shape with a moderate growth rate. Classified as peaceful, this species primarily occupies the mid-level and surface zones of the aquarium and produces a medium level of biological waste.
To thrive, the New Guinea Rainbowfish requires a freshwater only aquarium with a minimum volume of 110 litres and a tank length of at least 90 cm. Water temperature should be maintained between 22°C and 28°C, with a pH range of 6.5–8 and a general hardness of 5–15 dGH. A moderate water flow is preferred.
The New Guinea Rainbowfish is a rewarding species to keep, provided its core environmental needs are met. This species is available in 3 varieties: Standard / Unsexed, 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.
New Guinea Rainbowfish Habitat Setup
When setting up an aquarium for the New Guinea Rainbowfish, a moderate water flow best suits their natural preferences. Because this species occupies the mid-level and surface 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 light plant coverage for partial shade. Keepers should note that a tight-fitting lid is essential, as this species is a known jumper.
New Guinea Rainbowfish Compatibility Notes
Classified as peaceful, the New Guinea 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, shy or slow-feeding tankmates may be outcompeted at feeding time and their energetic swimming style may stress more sedentary or timid species. Selecting tankmates that favour different water layers from the mid-level and surface zones can help reduce competition and territorial overlap.
Who New Guinea Rainbowfish Is Actually For
New Guinea 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 New Guinea 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.
New Guinea Rainbowfish Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for New Guinea Rainbowfish.
30 Gallon Breeder
40 Gallon Breeder
55 Gallon Standard
60 Gallon Breeder
75 Gallon Standard
90 Gallon Standard
Show 10 more tank sizes
Frequently Asked Questions About New Guinea Rainbowfish
How big does New Guinea Rainbowfish get?
New Guinea Rainbowfish (Melanotaenia affinis) typically reaches a maximum adult size of approximately 11.5 cm. They have a compressed body shape and a moderate growth rate.
What tank size does New Guinea Rainbowfish need?
A minimum aquarium volume of 110 litres and a tank length of at least 90 cm are recommended for New Guinea Rainbowfish. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does New Guinea Rainbowfish need?
New Guinea Rainbowfish thrives in freshwater only conditions with a temperature range of 22–28°C, a pH between 6.5 and 8, and a general hardness of 5–15 dGH. A moderate water flow is preferred.
Is New Guinea Rainbowfish peaceful or aggressive?
New Guinea 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 New Guinea Rainbowfish should be kept together?
New Guinea 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 New Guinea Rainbowfish have any special tank requirements?
Yes. New Guinea Rainbowfish benefits from plants - lighly covered in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Does New Guinea Rainbowfish need a lid on the tank?
Yes. New Guinea 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 6, 2026
- Last updated
- May 6, 2026
- Issues or corrections?
- Contact the editorial team
Top Tank Mates for New Guinea Rainbowfish
These fish are strong compatibility matches for New Guinea Rainbowfish based on water preferences, temperament, adult size, and tank behavior.
Spotted Hillstream Loach
Gastromyzon punctulatus
Ideal Tank MatesTrapdoor Snail
Cipangopaludina chinensis
Ideal Tank MatesWhite Cheeked Goby
Rhinogobius duospilus
Ideal Tank MatesReticulated Stingray (Teacup Ray)
Potamotrygon orbignyi
Ideal Tank MatesTandanus Catfish
Tandanus tandanus
Ideal Tank MatesSkunk Cory
Corydoras arcuatus
Ideal Tank MatesPlants That Suit New Guinea Rainbowfish
These plants pair well with New Guinea Rainbowfish based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
African Onion Plant
Crinum calamistratum
Afzel's Anubias
Anubias afzelii
Anacharis
Egeria densa
Ashy Pipewort
Eriocaulon cinereum
Baby Tears
Lindernia rotundifolia
Balansae
Cryptocoryne crispatula
Fish Similar to New Guinea Rainbowfish
Silver Rainbowfish
Chilatherina crassispinosa
An active, schooling rainbowfish native to the clear, fast-flowing streams of Northern New Guinea. Known for their energetic swimming patterns and silvery bodies, they require long aquariums with strong water flow and high dissolved oxygen. Best kept in groups of 6 or more.
Barred Rainbowfish
Chilatherina fasciata
A robust, active, and highly colorful schooling fish native to the clear, fast-flowing streams of New Guinea. They are named for the distinctive vertical black bars on their lower flanks. As highly active swimmers that do best in hard, alkaline water, they require a spacious, long aquarium (minimum 4 feet) with strong oxygenation and plenty of open swimming space.
Eastern Rainbowfish
Melanotaenia splendida
An active, schooling species native to Australia, highly variable in color depending on the catch location. They are fast swimmers that require long tanks with ample open swimming space. Because of their energetic feeding behavior, they can outcompete shy or slow-moving fish. Best kept in shoals to display natural morning sparring and courtship behaviors.
Goldie River Rainbowfish
Melanotaenia goldiei
The Goldie River Rainbowfish is a vibrant, highly active schooling fish native to the clear rainforest streams and backwaters of southern New Guinea. As rapid swimmers, they require significant open swimming space. They are voracious mid-water and surface feeders that will readily eat insects and standard aquarium foods. While peaceful, their exuberant energy can intimidate shy tank mates.
Blue Rainbowfish
Melanotaenia caerulea
A small, highly active, and colorful schooling fish native to the Kikori River system in Papua New Guinea. They are peaceful but require ample swimming space and a school of their own kind to thrive. Like most rainbowfish, they appreciate well-oxygenated, flowing water and are excellent jumpers. Males develop a striking blue hue with reddish horizontal stripes.
Western Rainbowfish
Melanotaenia australis
An energetic, colorful schooling fish native to Northwestern Australia. They display prominent lateral zigzag lines and bright red or orange fins. Known for their active nature, they require plenty of horizontal swimming space and should be kept in schools to reduce stress and encourage males to display their best colors. They are boisterous feeders that may outcompete shy fish.