Boeseman's Rainbowfish
Melanotaenia boesemani
Boeseman's Rainbowfish (Melanotaenia boesemani) is undoubtedly the iconic species that made the Rainbowfish family famous in the aquarium hobby. Adult males offer an unparalleled chromatic spectacle: the front half of the body is a brilliant metallic blue-violet, while the rear half drastically fades into a vibrant fiery orange-red. Active, robust, and perpetually in motion, it brings an explosion of energy and color to the middle and upper parts of large community aquariums.
Water Temperature
24 - 28 °C
pH Value
7 - 8
Water type
Freshwater
Tank level
Surface and middle
Adult size
11 cm
Minimum tank volume
>= 250 L
Minimum group
>= 6
GH
10 - 20 dGH
KH
5 - 10 dKH
TDS
200 - 400 ppm
Conductivity
313 - 625 uS/cm
Species description
Geographical Origin and Habitat: Endemic to the Ayamaru Lakes (Papua, Indonesia). These karst lakes have crystal clear, alkaline waters rich in submerged aquatic plants.
Taxonomy and Morphology: Boeseman's Rainbowfish (Melanotaenia boesemani). The rainbowfish par excellence. The adult male has a high, massive and flattened body, with the two dorsal fins very close together.
Social Behavior: Gregarious, peaceful, tireless swimmer. Males exhibit their love parades (Flashing) lighting up with fluorescent colors to impress females at dawn, crossing each other at full speed.
Coloration and Sexual Dimorphism: Unmistakable "half-and-half" dichromatism: the head and the front part of the body are a metallic Blue-Violet, while the rear half (caudal peduncle included) is bright Yellow-Orange. Females remain more slender, silver and less brightly colored.
Care, breeding and tankmates
Aquarium Setup: Long tank (120 cm / 48 inches min) to allow school swimming. Leave the center completely clear for the parades. Stem plants and intricate roots should be confined to the back. Likes intense light and dark background to maximize colors.
Diet and Feeding: Water column omnivore. Needs natural carotene (Astaxanthin, Krill, Spirulina) to develop the orange half of the body. Insert frozen bloodworms and shrimp-based pastes.
Water Quality: Attention to the lakes of origin: the Ayamaru lakes are karst, therefore the water MUST be hard (GH > 10) and alkaline (Ph > 7.5). In soft and acidic water (like Amazonian), boesemani will waste away.
Compatibility and Cohabitation: Ideal fish for robust community tanks. Insert together with rainbowfish of the genus Glossolepis (G. incisus), Clown Loaches and Barbs. Due to their hyperactivity, do not associate them with Discus or excessively shy/slow fish.
Aquarium Breeding: Mop Spawner. Breeders drop a few eggs daily tangled in the vegetation with sticky filaments (they do not eat their offspring if well fed). The eggs take about 7-10 days to hatch.
Risks and Diseases: Juvenile disappointment. Very often sold at the juvenile or sub-adult stage, they appear as very sad "little gray fish". Many snub them; in reality they will take up to a year of excellent care to develop the glorious blue/orange colors.
Geographic Origin and Distribution
Endemic to the Ayamaru Lakes (Papua, Indonesia). These karst lakes have crystal clear, alkaline waters rich in submerged aquatic plants.
Origin
Tropical oceans and reefsSouth and Southeast AsiaEast AsiaAustralia, New Guinea, and Oceania
Fish profile
- Temperament
- Peaceful
- Their temperament is generally peaceful. Males frequently spar playfully without causing harm. They add dynamic energy to community tanks.
- Diet
- Omnivore
- They are naturally omnivorous. They readily accept flakes and small frozen foods. A varied diet enhances their vibrant colors.
- Life expectancy
- 5-8 years
- Boeseman's Rainbowfish has a lifespan of 5 to 8 years in captivity when provided with optimal conditions. To achieve this longevity, they require pristine, highly oxygenated water and a spacious tank to satisfy their active lifestyle. Maintaining stable water parameters, particularly harder alkaline water, is vital to prevent osmotic stress and disease. A stress-free environment with appropriate tankmates and a nutrient-rich diet will ensure they reach their full lifespan.
- Adult size
- 11 cm
- The catalog's scalar value is 11 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 9 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Melanotaenia boesemani (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- Group
- Keep one male to multiple females. This significantly reduces male harassment. Multiple males can coexist in larger aquariums.
- Feeding frequency
- Twice daily
- Feed small portions twice a day. They consume food rapidly from the surface. Avoid overfeeding to maintain water quality.
- Bioload
- Medium
- They produce a moderate bioload. Efficient filtration is needed for their active lifestyle. Regular water changes maintain pristine conditions.
- Flow
- Moderate
- They appreciate moderate to strong flow. This simulates their native river habitats. Good circulation is highly beneficial.
- Jump risk
- Yes
- There is a very high jump risk. A tight-fitting lid is absolutely essential. Many are lost to open tanks.
- Reproduction
- Oviparous
- They are prolific egg scatterers. Parents will eat eggs if not removed. Fry require extremely small initial foods.
- Compatibility & tankmates
- Community
- They are peaceful but highly active. Avoid housing with slow or timid species. They thrive with other energetic fish.
- Tank level
- Top/Middle
- They swim in the middle and upper levels. They require plenty of open swimming space. Perimeter plants provide security.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 2.9 ± 0.4 se
- Resilience
- Medium (1.4 - 4.4 years)
- Phylogenetic uniqueness (PD50)
- 0.5
- Bayesian Length-Weight
- a = 0.01122, b = 3.04
- VulnerabilityLow vulnerability (10 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
