Melanotaenia gracilis

Slender Rainbowfish

Classification

Melanotaeniidae

Distribution

North Western Australia. So far, it has been recorded only from the Drysdale and Carson Rivers in the Kimberley area.

Habitat

Slow-moving areas of these rivers. It’s also found isolated in surrounding pools during the dry season. The water in these habitats is typically very clear.

Maximum Standard Length

3″ (7.5cm).

Aquarium SizeTop ↑

30″ x 12″ x 12″ (75cm x 30cm x 30cm) – 70 litres.

Maintenance

Unlke many other members of the genus, the natural habitat of M. gracilis is quite sparse and rocky. A biotope aquarium would thus consist of a gravel substrate with smooth, water-worn rocks, and possibly the odd beech branch or two. However the fish are equally as happy in a densely planted setup. In either case, water movement should be kept to a minimum.

Water Conditions

Temperature: 72-82°F (22-28°C)

pH: 7.0-8.0

Hardness: 10-20°H

Diet

Unfussy and will accept most dried, frozen and live foods. Regular feedings of the latter will help to ensure the fish exhibit their best colours.

Behaviour and CompatibilityTop ↑

This is one of the smaller rainbowfish and is very peaceful. Good tankmates include other similarly-sized rainbowfish, characins, danios, barbs, freshwater gobies and catfish such as Corydoras. It can also be kept with many species of Rift Lake cichlid, due to its water requirements.

The slender rainbowfish can be quite skittish and does far better when kept in a shoal of at least 6-8, preferably more. The males will also be encouraged to display their best colours in the company of conspecifics.

Sexual Dimorphism

Mature males are larger and exhibit brighter colouration than females. They also develop a deeper body than females as they grow.

Reproduction

No information available, although we assume it has been achieved. It probably breeds in a similar fashion to other species in the genus, although the lack of aquatic vegetation in its natural waters may indicate that it scatters its eggs directly onto the substrate, as opposed to among the leaves of plants.

NotesTop ↑

This uniquely-shaped rainbow is an uncommonly seen species in the hobby, mainly because it hails from such a remote area in Australia. It is currently listed on the IUCN list of threatened species as being at risk, so all attempts at captive spawning are to be encouraged.