Melanotaenia australis

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Melanotaenia australis, also known as Western Rainbow, is an Australian rainbowfish valued for its activity and shifting colours. This hardy species belongs to the family Melanotaeniidae and is best kept in a group in a spacious aquarium. Its silvery body develops blue-green, bronze and golden reflections depending on lighting, mood and social position. Native to waterways in northwestern Australia, it inhabits environments where temperature can change considerably. Its generally peaceful nature, constant activity and willingness to accept varied foods make it an interesting choice for a well-planned community aquarium.

General species description

Melanotaenia australis is a medium-sized, active and schooling rainbowfish that should be kept in a group to display more natural behaviour. Adult males usually develop the strongest colours, especially while courting or establishing a hierarchy. The species mainly uses the open middle levels of the aquarium. It benefits from well-oxygenated water, efficient filtration and generous horizontal swimming space. Its temperament is generally peaceful but highly energetic; slow or very timid tank mates may be unsettled by its activity. A layout combining plants, open swimming areas and a few shelters suits this robust fish well.

Geographic origin and biotope

Melanotaenia australis is found mainly in northwestern Australia, particularly in Western Australia and adjoining areas of the Northern Territory. It inhabits rivers, creeks, billabongs and quiet areas connected with major Kimberley drainage systems. The biotope may include shaded banks, open stretches and edges covered with vegetation. Natural conditions change between the dry and wet seasons, bringing variation in water level, flow and temperature. In an aquarium, clean water, neutral to slightly alkaline conditions and good circulation better reflect its habitat than stagnant water.

Precise location and local name

The distribution includes the Fitzroy River basin, along with several waterways of the Kimberley and northwestern Australia. Populations are also associated with northern Australian drainage systems, depending on the boundaries used for the species. The most common English name in the aquarium trade is Western Rainbowfish, often shortened to Western Rainbow. The word “rainbowfish” refers to the iridescent reflections that appear on the flanks when light strikes the scales. Populations may differ in colour and body shape according to their drainage basin.

Appearance and physical characteristics

The body of Melanotaenia australis is elongated, fairly deep and laterally compressed, with large, reflective scales. A dark lateral band may be visible along the flank over a silvery, bluish or greenish background. The fins often become more colourful in males, showing yellow, orange or reddish tones. The dorsal fin is divided into two sections, a characteristic feature of rainbowfish. Adult males are generally larger and more intensely coloured, while females often have a slimmer profile and less developed fins. The commonly reported maximum size is about 10 to 12 cm.

General diet

Melanotaenia australis is an omnivore and benefits from a varied diet offered in small portions. In the wild, it takes terrestrial and aquatic insects, small crustaceans, zooplankton and various plant materials. In an aquarium, a quality flake or micro-pellet staple can be supplemented with frozen or live foods such as daphnia, brine shrimp and mosquito larvae. Plant-based foods also help balance the diet. Variety supports the colouration of males, growth and overall condition. Overfeeding should be avoided, and uneaten food should be removed promptly.

Essential data

• Name of original river: Fitzroy River and associated Kimberley waterways
• Local name used: Western Rainbowfish
• Origin of the scientific name: A name formed from Greek and Latin roots describing coloration and geographic origin.
• Etymology of the complete name: Melanotaenia means “black band”; australis means “southern” or “of the south”.
• Common/vernacular names: Western Rainbow, Western Rainbowfish, Western Australian Rainbowfish
• Family: Melanotaeniidae
• Subfamily: Melanotaeniinae
• Name pronunciation: mell-ann-oh-TAY-nee-ah - aw-STRAL-iss
• Discovery: François-Louis de Laporte, comte de Castelnau, 1875
• Maximum adult size: About 10 to 12 cm
• Water temperature and pH: 22 to 28 °C; pH 6.8 to 8.0
• Stream appearance and surrounding vegetation: Quiet to moderately flowing water, wooded or open banks, aquatic plants and riparian vegetation.
• Typical tank mates: Melanotaenia splendida inornata, Iriatherina werneri, Pseudomugil gertrudae
• Temperament and behaviour: Peaceful, schooling, active and sometimes competitive during courtship.
• Water depth: Shallow to medium-depth areas of rivers, margins and billabongs.
• Sexual dimorphism: Males are larger, deeper-bodied and more colourful; females are generally smaller and duller.
• Bottom structure and flow: Sand, gravel, silt or plant debris; variable flow, often gentle near the banks.

For greater success

To keep Melanotaenia australis successfully, provide a long, covered and well-filtered aquarium with open swimming space and plants around the edges. Keep it in a group to reduce nervousness and encourage natural behaviour. Stable, well-oxygenated water with low waste levels is essential. Offer small portions of varied foods and select peaceful tank mates able to match its pace. Males show their best colours under suitable lighting and within a balanced group, without overcrowding or excessive aggression.