Skip to content
Know your inhabitants. Start with their needs.
aquariumwebshop
Care guide · Freshwater · fish

Eastern rainbowfish

Melanotaenia splendida

Eastern rainbowfish (Melanotaenia splendida)
Photo: Jesse de Vries / iNaturalist, CC BY 4.0. Photo: Jesse de Vries / iNaturalist · Source · CC BY 4.0Resized and compressed; no cropping or colour changes.

The eastern rainbowfish (Melanotaenia splendida, eastern form) is an active Australian shoaling fish with striking local colour variation. Adult males are usually more brightly coloured than females and juveniles. It needs a long aquarium, a group of its own kind and open swimming space. Broad seasonal conditions in the wild are not a reason to fluctuate aquarium temperature continually. Names for local forms and subspecies are not used consistently by every source; this guide focuses on the eastern form and cannot identify an unlabelled, potentially mixed trade fish. Ask about provenance when a particular population matters to you. A spacious aquarium with an open swimming lane and stable water quality is more important than chasing an exact pH number.

Plan your aquarium →

At a glance

Temperature
25–28 °C
pH
7.0
GH
5–20 °dGH
Aquarium length
At least 120 cm
Minimum aquarium volume
At least 108 L
Adult size
Up to 15 cm
Group size
At least 6 individuals
Temperament
Peaceful

About this species

GBIF accepts Melanotaenia splendida (Peters, 1866) as a species in the family Melanotaeniidae. Eastern rainbowfish is commonly used for the eastern or nominate form, M. splendida splendida. FishBase and Seriously Fish treat several subspecies as valid, while the taxonomic treatment of some historical names differs among sources. Keep that uncertainty in mind when identifying fish. ANGFA describes local variation in body depth, colour and pattern, sometimes between river systems. Adult males are often deeper-bodied, more brightly coloured and develop longer dorsal and anal fin rays. Females and juveniles are generally more silvery and less strongly marked.

Natural habitat

The eastern form is reported from freshwater along the eastern side of Queensland’s Great Dividing Range, from southern coastal creeks north toward the Cape York region. It inhabits creeks, swamps, lagoons and rivers. Fish often shelter around aquatic vegetation and submerged timber, while also using open reaches. Temperature and water levels in Australia vary substantially by season; reported natural values around 20–30 °C and pH 5–8 describe habitat, not aquarium targets. Local populations can differ genetically and in appearance, so provenance is valuable, especially for breeding.

Aquarium and layout

Seriously Fish recommends a footprint of at least 120 × 30 cm for the eastern form and lists about 108 litres for a 120 × 30 × 30 cm tank. That volume follows from those dimensions and does not guarantee that every group fits. Choose a longer and larger aquarium for bigger groups or large adults. Keep at least six conspecifics, preferably six to eight or more when space permits. Dense marginal planting, wood and some sheltered areas provide cover; retain a long, open swimming lane. Provide effective filtration, oxygen exchange, slow to moderate flow and a secure lid, as active rainbowfish may jump.

Water conditions

For long-term aquarium care, Seriously Fish gives about 25–28 °C (77–82 °F), near-neutral pH and GH 5–20 dGH. The profile also lists a broad seasonal range in nature; do not confuse that with its aquarium recommendation. Avoid chasing an artificially exact pH if the fish are stable in otherwise suitable water. Stability, a mature filter, low waste and gradual acclimation matter. Measure conditions and avoid abrupt corrections. GH is not KH; the species source does not give a specific maintenance range for KH.

Behaviour and group size

This rainbowfish is described as peaceful, but it is large and fast-moving. It may unsettle smaller or slower fish even when water parameters overlap. Keep a social shoal of at least six; a lone fish or undersized group may remain skittish. Males display more readily with conspecifics. Local forms differ and related forms may hybridise. To preserve a local line, buy fish with known provenance and keep lines separate. We do not list a particular fish as a guaranteed tankmate without evidence for that exact pairing.

Feeding

The species-specific care source says Melanotaenia splendida accepts many dried, frozen and live foods. Offer a complete dry food the fish can readily take and vary it with suitable small animal foods. Existing complete flakes are linked as one part of a varied diet; dried daphnia is only an occasional supplement. Feed small portions that the whole shoal can reach and remove leftovers. Live or frozen foods may support condition and colour, but do not rely on a single prey type. Fry need much finer foods than adults.

Breeding

This is an egg-scattering fish: eggs are deposited singly or in small numbers and attached to plants or other surfaces by adhesive threads. Fine-leaved plants or a spawning mop can provide a laying surface. Seriously Fish notes that a separate breeding aquarium can make eggs and fry easier to manage; parents provide no dependable care. The source gives slightly harder, alkaline water around pH 7.5 and 26.5–29 °C for directed breeding. That is breeding context, not a reason to change the main aquarium abruptly. Check the spawning material regularly. Tiny larvae first need very fine food and later larger free-swimming foods. Retain locality labels and prevent mixing if preserving a particular form matters.

Sources & review

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

View the sources