Melanotaenia maccullochi

Dwarf Rainbowfish

Classification

Melanotaeniidae

Distribution

Papua New Guinea, Australia.

Habitat

It’s found over a surprisingly wide range of biotopes, from clear, flowing streams to still, turbid ponds stained with tannins. Water chemistry also varies wildly across these habitats, making this an adaptable species (see water parameters below). The fish usually congregate around areas of cover, such as aquatic vegetation or submerged logs and branches.

Maximum Standard Length

2.8″ (7cm), although it usually doesn’t attain this in aquaria.

Aquarium SizeTop ↑

24″ x 12″ x 12″ (60cm x 30cm x 30cm) – 55 litres.

Maintenance

This little rainbowfish is ideally suited to a heavily planted setup, and will show its best colours in such surroundings. Water flow should be quite slow, and this will also benefit the plants. Allow open spaces between areas of planting to allow swimming space and areas for males to display at one another. High water quality is essential to the well-being of this species, so weekly partial water changes are recommended.

Water Conditions

Temperature: 68-86°F (20-30°C)

pH: 5.5-8.0, depending on collection locality.

Hardness: 8-15°H

Diet

Like most of its congeners, it’s an unfussy, omnivorous species, 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 ↑

Very peaceful and suitable for many communitgy aquaria, given its adaptibility regarding water chemistry and relatively small size. Good tankmates include other similarly-sized rainbowfish, characins, danios, barbs, dwarf cichlids, freshwater gobies, and catfish such as Corydoras.

Like other rainbowfish, it 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 more colourful and have longer dorsal and anal fins than the deeper-bodied females.

Reproduction

As with other members of the genus, this is not a difficult species to breed, being an egg scatterer, although the fry can prove somewhat tricky to raise. The breeding aquarium should be at least 30″ long, and contain slightly hard, alkaline water with a pH of around 7.5 and a temperature of 80-84°F. A small air-powered filter will provide sufficient oxygenation and flow. The tank should be filled with fine-leaved plants such as java moss, or nylon spawning mops. No substrate is necessary.

The adult fish are best conditioned in a group in a separate aquarium, with plenty of live and frozen foods. As the fish come into condition, the females will appear noticeably plumper, and males will display to each other almost constantly. Select the fattest, best-coloured pair for spawning and introduce them to the spawning tank. A small raise in temperature can often induce spawning. The pair will spawn for a period of several weeks, laying batches of eggs each day. These are attached to surfaces by a small thread. Although the adults tend not to eat the spawn, it’s easier to raise the fry in a separate aquarium, so we recommend checking the plants or mops regularly and removing any eggs you find to a raising tank containing water from the spawning tank.

The eggs hatch in 7-12 days, depending on temperature, and the tiny fry initially require infusoria–type food, before graduating onto free swimming foods, such as brine shrimp nauplii, after a week or so. Sinking foods are unsuitable as the fry tend to stay very close to the water surface.

NotesTop ↑

There are a few geographical variants of this species available, which differ in colour, patterning and less commonly, size. These should not be mixed in aquaria, as they may hybridise. The differences are so apparent between some of these forms that they may well turn out to be different species in the future.