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Care guide · Freshwater · fish

Parkinson's rainbowfish

Melanotaenia parkinsoni

Parkinson's rainbowfish (Melanotaenia parkinsoni)
Photo: Phalinn Ooi / CC BY 2.0, via Wikimedia Commons. Photo: Phalinn Ooi / Wikimedia Commons · Source · CC BY 2.0Resized and compressed; no cropping or colour changes.

Parkinson's rainbowfish (Melanotaenia parkinsoni) is a striking, active shoaling fish from Papua New Guinea. Adults develop orange to red colour patches and swim mainly in the middle and upper aquarium levels. The species needs warm water and ample swimming space, and LICG does not classify it among the easiest rainbowfish for beginners. Keep it in a suitably large group, with cover along the margins and open swimming room. Prefer captive-bred fish and ask about the water conditions in which they were raised. Check the name, provenance and health of the fish when buying, and allow the shoal time to acclimate calmly.

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At a glance

Temperature
26–30 °C
pH
7.0–8.0
GH
8–15 °dGH
Aquarium length
At least 150 cm
Minimum aquarium volume
At least 300 L
Adult size
Up to 15 cm
Group size
At least 6 individuals
Temperament
Peaceful

About this species

The accepted name is Melanotaenia parkinsoni Allen, 1980, in the family Melanotaeniidae. It was named for R. Parkinson, who collected the first specimens. Adult colour varies; males generally develop stronger orange-red markings and a deeper body than females. LICG lists a total length of about 10–15 cm. This is total length, including the tail fin, not standard length. Do not confuse it with closely related rainbowfish that can look similar; the scientific name and provenance help confirm identity.

Natural habitat

The species is known from a few localities along the southeast coast of Papua New Guinea, including tributaries of the Kemp Welsh River and the area near Alotau. Allen described small streams and pools in grassy plains with patches of rainforest, submerged wood and branches. At one described pool, 27–30°C and pH 7.6–7.8 were recorded. These are field measurements, not a complete aquarium prescription. Its known range appears restricted and its IUCN status is Near Threatened. Prefer captive-bred fish where possible and never release aquarium animals outdoors.

Aquarium and layout

This medium to large rainbowfish swims actively and needs a long aquarium. LICG advises at least 150 cm for the largest rainbowfish that can reach about 15 cm; this guide applies that cautious general recommendation to this species. A specialist aquarium profile lists around 300 litres, but volume alone does not show whether a tank is long enough. Keep at least six together, with adequate room for the whole shoal. Plant mainly along the back and sides and retain a long swimming lane. Use a secure lid because startled rainbowfish may jump.

Water conditions

LICG's species table gives 26–30°C, pH 7–8 and GH 8–15 dH. Natural field sites have recorded 27–30°C and pH 7.6–7.8. Those field observations overlap the aquarium guidance but do not show that fluctuations are desirable. Keep temperature and water quality stable, measure with reliable tests and acclimate new fish gradually. Ask the breeder about the established water conditions. GH and KH are different measurements; the species table does not give a separate KH target.

Behaviour and group size

Parkinson's rainbowfish are active shoaling fish. LICG stresses that rainbowfish need enough room to swim as a group and that larger, more active species can disturb small, quiet tankmates. A group of six or more is a common species-specific aquarium recommendation; ensure the tank is spacious enough for them. We do not list individual companions as guaranteed matches. Consider adult size, swimming level, temperament and feeding competition. Avoid mixing different Melanotaenia species because closely related forms may hybridise in aquaria.

Feeding

This omnivore eats small insects and other animal foods in nature; rainbowfish also take algae and plant material. LICG recommends variety with quality dry food, frozen or live foods, and occasional plant-based items such as algae. Offer flakes or granules that the fish can readily take, alongside appropriately sized prey. An existing complete flake food is linked as one component, not as an exclusive diet. Dried Daphnia is only a supplement. Distribute food so the whole shoal can feed and remove leftovers.

Breeding

Rainbowfish attach adhesive eggs among fine-leaved plants, algae or a spawning mop. For planned breeding, a separate tank with suitable fine material and a sponge filter can help. Eggs may be moved to a rearing tank after spawning to reduce predation. LICG describes repeated small batches across the family; exact counts and hatching time vary by species and temperature. Do not present family-level figures as proven specifics for every Parkinson's rainbowfish. Maintain stable water quality in the rearing tank; newly hatched larvae need very fine food first.

Sources & review

This care guide draws on several specialist sources and was last checked on .

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