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.
Blue Rainbowfish At a Glance
Blue Rainbowfish Tank Requirements
Will Blue Rainbowfish fit in your tank?
Care guides tell you what Blue Rainbowfish needs, the next question is whether your tank can safely provide it. Test Blue Rainbowfish against your tank size, maintenance needs, and the fish you already keep before you buy.
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Blue Rainbowfish Water Parameters
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Blue Rainbowfish Temperament & Compatibility
Blue Rainbowfish Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Male
Males develop a much deeper body profile, an elongated first dorsal fin that overlaps the second, and vivid blue/red coloration[1][2]. They frequently display to females and rival males, which is a harmless, stylised behavior to establish dominance[3].
Differs in 2 traits from base species
Also known as: Male Blue Rainbowfish, Standard
Female
Females are noticeably smaller, more slender, and lack the intense coloration and elongated fins of the males[1][2]. Maintaining at least 2 females per male helps disperse the males' vigorous breeding attempts and reduces stress.
Differs in 1 trait from base species
Also known as: Female
Blue Rainbowfish Care Guide Summary
The Blue Rainbowfish, scientifically known as Melanotaenia caerulea, belongs to the Rainbowfish family group. Adults reach a maximum size of approximately 8 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 low level of biological waste.
To thrive, the Blue 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 24°C and 28°C, with a pH range of 7–8 and a general hardness of 5–15 dGH. A moderate water flow is preferred.
The Blue 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.
Blue Rainbowfish Habitat Setup
When setting up an aquarium for the Blue 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 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.
Blue Rainbowfish Compatibility Notes
Classified as peaceful, the Blue 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 mid-level and surface zones can help reduce competition and territorial overlap.
Blue Rainbowfish Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Blue Rainbowfish.
30 Gallon Breeder
40 Gallon Breeder
55 Gallon Standard
60 Gallon Breeder
75 Gallon Standard
90 Gallon Standard
Show 10 more tank sizes
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Frequently Asked Questions About Blue Rainbowfish
How big does Blue Rainbowfish get?
Blue Rainbowfish (Melanotaenia caerulea) typically reaches a maximum adult size of approximately 8 cm. They have a compressed body shape and a moderate growth rate.
What tank size does Blue Rainbowfish need?
A minimum aquarium volume of 110 litres and a tank length of at least 90 cm are recommended for Blue Rainbowfish. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Blue Rainbowfish need?
Blue Rainbowfish thrives in freshwater only conditions with a temperature range of 24–28°C, a pH between 7 and 8, and a general hardness of 5–15 dGH. A moderate water flow is preferred.
Is Blue Rainbowfish peaceful or aggressive?
Blue 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 Blue Rainbowfish should be kept together?
Blue 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 Blue Rainbowfish have any special tank requirements?
Yes. Blue Rainbowfish benefits from plants - densely covered in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Does Blue Rainbowfish need a lid on the tank?
Yes. Blue 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.
Top Tank Mates for Blue Rainbowfish
These fish are strong compatibility matches for Blue Rainbowfish based on water preferences, temperament, adult size, and tank behavior.
Dainty Cory (Salt and Pepper Cory)
Corydoras habrosus
Ideal Tank MatesZebra Shovelnose (Tigrinus Catfish)
Brachyplatystoma tigrinum
Ideal Tank MatesEmerald Green Cory
Corydoras splendens
Ideal Tank MatesAngelicus Botia
Botia kubotai
Ideal Tank MatesGolden Bristlenose Pleco
Ancistrus sp. L144
Ideal Tank MatesAgassiz Cory
Corydoras agassizii
Ideal Tank MatesPlants That Suit Blue Rainbowfish
These plants pair well with Blue 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 Blue Rainbowfish
Celebes Rainbowfish
Marosatherina ladigesi
An active, schooling fish native to the karst (limestone) streams of Sulawesi, Indonesia. Known for their striking neon blue lateral stripes and yellowish fins. They strictly require hard, alkaline water to thrive and are highly sensitive to soft, acidic conditions. A peaceful species that requires plenty of open swimming space.
Axelrod's Rainbowfish
Chilatherina axelrodi
A highly active, colorful schooling fish native to Papua New Guinea. Known for a bluish-grey upper body and yellowish-white lower body divided by a dark lateral stripe. Like most rainbowfish, they are incredibly fast, active swimmers that require pristine water, moderate flow, and significant horizontal swimming space.
Bulolo Rainbowfish
Chilatherina bulolo
A rare and highly active rainbowfish native to the fast-flowing mountain streams and white-water rapids of the Markham and Ramu river systems in Papua New Guinea. They possess a silvery body with a distinct black streak on the upper and lower edges of the caudal fin. Because of their specialized natural habitat, they require highly oxygenated, fast-flowing water and alkaline conditions to thrive in an aquarium.
Turquoise Rainbowfish
Melanotaenia lacustris
A stunning, deep-bodied rainbowfish endemic to Lake Kutubu in Papua New Guinea. Famous for their ability to shift colors from deep teal to bright iridescent blue depending on mood and water quality. They are active schooling fish that thrive in hard, alkaline water.
Allen's Rainbowfish
Chilatherina alleni
A rare and highly active rainbowfish native to West Papua, Indonesia (Wapoga River basin). Known as the 'Wapoga Rainbowfish', they undergo a dramatic color transformation as they mature, developing intense metallic blues, greens, and reds. As exceptionally fast, continuous swimmers, they require a 4-foot (120cm) aquarium minimum to thrive without stress.
Bleher's Rainbowfish
Chilatherina bleheri
A stunning, highly active schooling fish endemic to Lake Holmes (Danau Bira) in Papua, Indonesia. Known for its distinct dual-coloration, with the front half being greenish-blue and the back half turning a vibrant red/orange. They are famously active darters and require long tanks with significant open swimming space and well-oxygenated water.