Western Rainbowfish - Melanotaenia australis
Western Rainbowfish - Melanotaenia australis

Western Rainbowfish - Melanotaenia australis

The Western Rainbowfish was collected from a stream in north-western Australia during the early 1870’s by a minister named Bostock. It was scientifically described in 1875 by Castelnau and its scientific name is Melanotaenia australis. It has also been known as Melanotaenia splendida australis.

The Western Rainbowfish can reach a length of 11 cm. The Western Rainbowfish is known for its characteristic pair of zigzagging blackish lines that can be seen on the lower sides of the body, right above the anal fin. The main colouration varies a lot between the various populations, especially when it comes to the fins. The most frequently found body colour combination is a brownish or olive coloured back, a diffuse mid-lateral stripe and then white on the lower part of the body. Many fishes display narrow reddish striping between the horizontal scale rows. In some populations the mid-lateral stripe is certainly not diffuse; it’s really prominent. In other populations, the mid-lateral stripe can hardly be seen at all. If you keep a Western Rainbowfish with a distinct mid-lateral stripe, it might hail from King George River or South Alligator River. If the mid-lateral stripe is double, you are probably looking at a fish from Drysdale River, especially if the fish is smaller than other Western Rainbowfishes.  If your fish has hardly any mid-lateral stripe at all, it might instead belong to a population from the Pilbara region.

Geographical distribution, habitat and conservation
Western Rainbowfish is chiefly found in Western Australia, but you can also find them in the westernmost parts of the Northern Territory. In Western Australia, Melanotaenia australis lives in both Kimberley and Pilbara. The Kimberley and Pilbara populations do not intermingle with each other since there are no permanent streams running between Kimberley and Pilbara. In the Northern Territory, Western Rainbowfish is common west of Darwin and scarce east of Darwin.

The Western Rainbowfish lives in lakes, pools in drying streambeds, marshy lagoons, marshlands, creeks and rivers. Ideally include driftwood and live plants in the aquarium since the Western Rainbowfish is known to appreciate such features in the wild. The largest groups can be found in slow mowing waters and strong current is therefore not recommended in the aquarium. When living in deeper pools it seldom ventures into the depths, it prefers to stay close to the surface. When living in lakes and swamps, Western Rainbowfishes are known to seek out the shallow edges.

Western Rainbowfish
Western Rainbowfish - Melanotaenia australis
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In the wild, Western Rainbowfish is often found in environments that are highly affected by seasonal variations. The pH-value can for instance shift from 6.0 to 8.0, especially in rivers that have their headwaters in limestone regions. As you might have guessed, these fishes are also used to significant changes in water hardness. In the aquarium, it is however a bad idea to expose your fish to sudden changes in water quality. Slow and gradual changes are the safest way to go. If you really want to make your Western Rainbowfish feel at home, keep them in hard water from April through October and then gradually make the water softer for the “wet season”.  

The Western Rainbowfish has not been evaluated by the IUCN Red List of Threatened Species. It is believed to be one of the most abundant species of Rainbowfish in Australia.

Keeping Western Rainbowfish in aquariums
The Western Rainbowfish is very popular among Rainbowfish keepers since it is an adaptable species that can be kept even by beginners. When keeping Western Rainbowfish, it is best to keep several females for each male. Keep the water temperature in the 23-32 degrees C (73-90 degrees F) range. The Western Rainbowfish can adapt to both acidic and alkaline waters, but avoid letting the pH-value drop under 6.5 or rise above 7.7. Some aquarists have reported how soft blackwater have caused their Western Rainbowfishes to develop brighter colours. When tampering with the water conditions, it is advisable to make the changes fairly slow and gradual.  

Breeding Western Rainbowfish
Western Rainbowfish will readily breed in groups and reaches sexual maturity when they are around 4 cm (1 ½ inches) long. If you want to set up a separate breeding aquarium, 30 litres (8 gallons) is large enough. Once you have managed to get your Western Rainbowfish into breeding condition, eggs will often be deposited every day. This species normally spawns during the early morning hours and will use bushy plants as spawning medium. You should therefore include java moss or similar in the set up, or give your fish special spawning mops. If the parents are well fed and the java moss thick, you don’t have to remove the eggs to a separate container. The fry can be fed infusoria and powdered flake food until they are large enough to eat newly hatched brine shrimp.  

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Chequered Rainbowfish
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Banded Rainbowfish
Ornate Rainbowfish