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The Australian Rainbow (Melanotaenia fluviatilis) is sometimes known as the Murray River Rainbow. They originate from Australian waterways such as rivers, lakes and streams, in areas where the water is relatively still and clear, but with thick vegetation. In the wild they are omnivorous so eat a diet of both aquatic and terrestrial invertebrates as well as filamentous algae. They group around logs or grassy banks and exhibit schooling behaviour in groups of 5 or more.
They are a very colourful fish (Rainbow), the males more so than the females. If their vegetation or substrate is dark in colour then the fish will darken. Their sides are a silvery-brown with a green or blue tinge. They have a blue stripe down their length and their yellow tails often have orange or red markings. While they can grow to a maximum length of 4.3 inches (11cm), the males usually grow up to 3.3 inches (8.5cm) and the females smaller at up to 2.8 inches (7cm).
They are a schooling fish and best kept in groups of 6 or more (if less than 6 choose one sex only), for larger groups better to have same number of males and females or more females than males e.g. 3 males plus 4 or 5 females. Australian Rainbowfish keep well in a large aquarium with other similar sized fish.
They like dense vegetation to hide in but they also need free swimming areas. As they are omnivorous they may nibble the plants, so live would be preferred. A gravel substrate will mimic their natural habitat. A tank size minimum of 30 gallons (114 litres) will provide for plenty of free swimming space. A temperature range between between 70-79F (21-26C) is ideal. In natural habitat they like to hide behind logs so traditional aquarium furniture or areas of dense plants will be used well.
Australian Rainbows are omnivores. In captivity they will happily feed on fish flakes and live food. Their colours will be brighter if there is live food in their regular diet.