Axelrod's rainbowfish
Chilatherina axelrodi
A Papuan rainbowfish with blue-silver and yellow reflections, with sleek elegance and active swimming in the mid-to-upper zone. Prefers slightly alkaline, warm water (26–30 °C), an exception compared to many more common tropical fish. In schools of 6–8+ with proper lighting, males display brilliant colorations during morning displays. An adaptable omnivore that in nature also consumes filamentous algae — a useful detail for planted tanks. Breeding is not difficult, but water quality must be excellent and consistent.
Water Temperature
25 - 29 °C
pH Value
7.5 - 8.2
Water type
Freshwater
Tank level
Middle
Adult size
10 cm
Minimum tank volume
>= 150 L
Minimum group
>= 6
GH
10 - 18 dGH
KH
5 - 9 dKH
TDS
200 - 360 ppm
Conductivity
313 - 563 uS/cm
Species description
Geographical Origin and Habitat: Endemic to the Yapsei river (a tributary of the Sepik) in Papua New Guinea. Lives in a narrow river basin covered by calcareous forest: the waters of the stream are hard and alkaline.
Taxonomy and Morphology: Axelrod's Rainbowfish (Chilatherina axelrodi). Reaches 10 cm (4 inches), laterally compressed body and pointed snout-dorsal profile. Large and rigid scales compared to other genera.
Social Behavior: Feverish swimmer, rarely relaxes. Like all Melanotaeniids it needs a hierarchical structure within a large school (more males in exhibitionistic competition distract a single male from oppressing the females).
Coloration and Sexual Dimorphism: Iridescent males: yellowish-brown back, lower half of the body with a thick fragmented black-blue lateral bar emerging behind the pectorals. Bright yellow odd fins. Silvery or greenish, drab females.
Care, breeding and tankmates
Aquarium Setup: Minimum 120 cm (48 inches) given the hyperactivity and sudden accelerations. Excellent use of calcareous pebbles to keep the pH high, combined with strong currents (movement pumps) and rocks surfacing.
Diet and Feeding: Voracious omnivore of mid and high tank. Flake foods with a strong plant component (Spirulina, Chlorella) recommended, supplemented with frozen krill or bloodworms.
Water Quality: One of the freshwater species that most needs dissolved minerals: pH 7.5-8.2 and high hardness (GH 10-18). Using reverse osmosis for this fish will lead to the collapse of its immune defenses.
Compatibility and Cohabitation: Ideal companion for community tanks of hard water fish, even mild Central American Cichlids or not too fierce Victorian Cichlids. Perfect with Melanotaenia boesemani.
Aquarium Breeding: The male flashes a luminescent stripe on its forehead ("blaze") during courtship, leading the female towards the moss skein (or wool threads). Large eggs but slow to hatch (up to 15 days at 25°C / 77°F).
Risks and Diseases: The absence of females in shops (because they are "ugly") causes many aquarists to buy only males. An all-male school will become hysterical, triggering stress pathologies (cutaneous bacteriosis).
Geographic Origin and Distribution
Endemic to the Yapsei river (a tributary of the Sepik) in Papua New Guinea. Lives in a narrow river basin covered by calcareous forest: the waters of the stream are hard and alkaline.
Origin
Africa and MadagascarAustralia, New Guinea, and Oceania
Fish profile
- Temperament
- Peaceful
- They are peaceful, highly gregarious, and intensely social schoolers. A group of six or more is absolutely essential always. Their coordinated movements create a truly breathtaking visual display.
- Diet
- Omnivore
- They are enthusiastic omnivores requiring a well-balanced daily diet. Premium flakes, live daphnia, and frozen brine shrimp work perfectly. Vegetable matter is crucial for their health and brilliant hues.
- Life expectancy
- 4-8 years
- The average lifespan for this species is 4 to 8 years in a well-managed aquarium. Constant partial water changes and a rich, varied diet are critical factors in preventing disease and extending lifespan. A healthy environment stimulates consistent color displays.
- Adult size
- 10 cm
- The catalog's scalar value is 10 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 7 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Chilatherina axelrodi (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
- School
- Maintaining an appropriate sex ratio is critical for the long-term harmony of a Chilatherina axelrodi shoal. It is highly advised to keep significantly more females than males (usually a 1:2 or 1:3 male-to-female ratio) to disperse the males' constant, energetic breeding displays. While a group featuring multiple males will result in breathtaking 'flashing' colors as they compete for attention, there must be enough females to prevent any single fish from being harassed to exhaustion. Purchasing a sufficiently large initial school allows for the natural expression of these vibrant social dynamics.
- Feeding frequency
- Twice daily
- Two small daily meals perfectly maintain their high energy. They are aggressive surface feeders splashing water during meals. Uneaten food must be avoided to prevent sudden ammonia spikes.
- Bioload
- Medium
- Axelrod's rainbowfish contribute a moderate, manageable freshwater bioload. Rapid digestion requires a fully mature biological filter always. Regular maintenance ensures their vibrant scales remain completely pristine.
- Flow
- Moderate
- They deeply appreciate a strong, continuous, and dynamic water current. Filter returns should simulate their natural fast-flowing river habitats. Vigorous flow keeps them fit and encourages tight schooling.
- Jump risk
- Yes
- Axelrod's rainbowfish possesses a very high risk of jumping, intrinsic to its streamlined morphology and high-velocity swimming nature. In the wild, they are accustomed to evading predators or snatching low-flying insects by breaking the water's surface. In captivity, sudden noises, aggressive mating chases, or even just turning the tank lights on can trigger a panicked skyward dash. To prevent these beautiful fish from fatally leaping out, a tightly sealed hood or heavy glass cover is an absolute requirement.
- Reproduction
- Oviparous
- They breed readily, scattering eggs continuously among dense vegetation. Males develop intensely bright courting stripes during morning hours. Infusoria is strictly required to feed the exceptionally tiny fry.
- Compatibility & tankmates
- Verify
- They are a wonderfully peaceful species for mixed communities. They thrive with robust, similarly sized active swimming fish. Avoid aggressive fin-nippers that damage their delicate beautiful finnage.
- Tank level
- Middle
- These energetic rainbowfish are classic top-to-midwater dwellers, favoring the expansive, brightly lit upper strata of the aquarium. They swim with almost ceaseless forward momentum, requiring long, uninterrupted swimming lanes directly below the surface. While they will sink to mid-level to feed on sinking pellets or display to rivals, they quickly return to patrolling the top third of the tank. Dense planting should be kept to the perimeter to ensure the central upper water column remains completely unobstructed.
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)
- 0.5005
- Bayesian Length-Weight
- a = 0.00389, b = 3.12
- 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.
