Dwarf rainbowfish - Melanotaenia maccullochi

Scientific name: Melanotaenia maccullochi

Common name: Dwarf rainbowfish

Family: Melanotaeniidae

Usual size in fish tanks: 6 - 7 cm (2.36 - 2.76 inch)

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Recommended pH range: 5.5 - 7.5

Recommended water hardness: 8 - 18°N (142.86 - 321.43ppm)

0°C 32°F30°C 86°F

Recommended temperature range: 22 - 28 °C (71.6 - 82.4°F)

The way how these fish reproduce: Spawning

Where the species comes from: Oceania

Temperament to its own species: peaceful

Temperament toward other fish species: peaceful

Usual place in the tank: Top levels

Food and feeding

Dwarf rainbowfish (Melanotaenia maccullochi) are omnivores and thrive on a balanced diet of both animal and plant-based foods. Offer them quality flakes or micro-pellets as a staple, but regularly supplement with live or frozen foods such as brine shrimp, daphnia, and bloodworms. Adding spirulina-based flakes or blanched vegetables helps with digestion and enhances coloration.

Origin

This species originates from Northern Australia and Papua New Guinea, where it inhabits slow-moving streams and densely vegetated waterways.

Sexing

Males are noticeably more colorful, often displaying vibrant shades of red, blue, and green. They also have more elongated fins, while females remain smaller with subtler coloration.

Breeding

Breeding Melanotaenia maccullochi is relatively straightforward. Condition pairs with live foods, and they will scatter eggs among fine-leaved plants or spawning mops. Remove the parents after spawning to protect the eggs. Incubation lasts 7–10 days, and the fry should initially be fed with infusoria before transitioning to newly hatched brine shrimp.

Lifespan

With proper care, the dwarf rainbowfish lives for about 3–5 years in aquariums.

Tank requirements

Tank size: Minimum 80 liters; larger if keeping a bigger school.
Setup: Provide dense planting, driftwood, and open swimming areas.
Water: Soft to moderately hard, pH between 5.5 and 7.5, temperature 22–28 °C.
Lighting: Moderate; brighter lighting enhances their natural colors.

Tankmates

Dwarf rainbowfish are peaceful, active shoalers. Choose tankmates of similar size and temperament that won’t outcompete them at feeding time or nip fins.

Ideal: other small rainbowfish (same species/locale), larger rasboras (e.g., Trigonostigma spp.), larger tetras (e.g., Hyphessobrycon spp.), Corydoras, small peaceful plecos (e.g., Ancistrus), mild gouramis (Pearl, Honey).
Avoid when possible: aggressive or strongly territorial cichlids, fast fin-nippers (some barbs), and very slow long-finned species that may be stressed by rainbowfish activity.
Group: keep 6 individuals (ideally a higher headcount with more females than males) to diffuse hierarchy and encourage full color display.

Plants

Aim for densely planted sides and background with clear swimming lanes at the front. Plants improve comfort, stability, and aesthetics; layered planting also breaks sightlines and reduces group stress.

Easy and hardy: Vallisneria, Hygrophila spp., Ludwigia spp., Ceratophyllum demersum (hornwort), Limnophila sessiliflora.
Epiphytes on décor: Java fern (Microsorum), Anubias spp., Bucephalandra — attach to roots/driftwood and rocks.
Floating plants: Salvinia, Pistia, Phyllanthus fluitans — provide gentle shade and boost colors; leave open surface areas for feeding and gas exchange.
Layout tip: plant the sides and back, keep the center as an open lane; combine with roots and stones for natural zoning.

Short description

The dwarf rainbowfish is a peaceful, social schooling fish that should be kept in groups of at least six, ideally with a higher ratio of females to males. It does well in community tanks with other peaceful species such as tetras, corydoras, and other small rainbowfish. Males may display to one another, but aggression is minimal if space is sufficient.