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Care guide · Freshwater · fish

Banded rainbowfish

Melanotaenia trifasciata

Banded rainbowfish (Melanotaenia trifasciata)
Photo: coenobita / iNaturalist, CC BY 4.0. Photo: coenobita (iNaturalist) · Source · CC BY 4.0Resized and compressed; no cropping or colour changes.

The banded rainbowfish (Melanotaenia trifasciata) is an active, robust rainbowfish from northern Australia. Colour and body shape vary markedly between river systems, so hobbyists often use a locality name alongside the species name. Juveniles are usually less striking than mature males. This species needs a long aquarium, a group of its own kind and generous open swimming space. Its broad natural seasonal temperature range is not a reason to let aquarium conditions fluctuate continually: choose a stable maintenance range. Different rainbowfish forms may also crossbreed. If you are maintaining or breeding locality lines, keep groups of known origin separate.

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At a glance

Temperature
27–29 °C
pH
6.5–8.0
GH
8–20 °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

The accepted name is Melanotaenia trifasciata (Rendahl, 1922), in family Melanotaeniidae and order Atheriniformes. The name literally means three-banded, although patterning is variable. ANGFA describes a deep body and sometimes interrupted dark lateral band; populations can differ in colour and shape. Mature males are generally larger and deeper-bodied, with longer dorsal and anal fins and stronger colour. Females tend to be slimmer with shorter fin rays. ANGFA reports a maximum around 15 cm but says most are under 12 cm; FishBase gives a smaller maximum standard length and a common length of 8 cm. Treat 15 cm as a reported upper size, not the typical adult length.

Natural habitat

Its discontinuous range spans northern Australia: from the Mary River and Arnhem Land in the Northern Territory, around the Gulf of Carpentaria to Cape York and parts of Queensland. It occurs in varied freshwater habitats, including slow streams, swamps, lagoons, pools and clear rivers. Fish are often found near aquatic vegetation, submerged branches and wood over sand, gravel or rock. Seasonal change affects temperature and water levels; ANGFA describes natural temperatures around 24–33 °C. Those are habitat observations, not advice to swing aquarium temperature over the same range. Keep locality names with captive-bred lines so colour forms are not mixed inadvertently.

Aquarium and layout

Seriously Fish recommends a footprint of at least 120 × 30 cm and gives about 108 litres for a 30 cm tank height. That volume is only the arithmetic capacity of those dimensions; it does not guarantee that every stocking plan is suitable at 108 litres. For an active group of six or more, a larger, longer aquarium is preferable and should account for adult swimming space. Plant the edges and corners densely but leave a broad, straight swimming lane. Wood and robust plants provide cover. Use a secure lid because active rainbowfish can jump. Flow may be slow to moderate; distribute the outlet so calmer areas remain. Keep locality lines separate if you intend to preserve pure breeding stock.

Water conditions

For aquarium care, Seriously Fish gives approximately 27–29 °C as a useful stable range, pH 6.5–8 and GH 8–20 dGH. Quick facts also show seasonal natural values up to 33 °C; that is not a necessary heater setting. FishBase and ANGFA describe different field measurements and locations, including cooler or more acidic conditions. Such observations are not the same as a long-term aquarium recommendation. Keep water stable and suited to the group’s provenance, test your source water and acclimate gradually. Avoid rapid pH correction or large temperature swings. Maintain ammonia and nitrite at zero and service filtration for the active stocking.

Behaviour and group size

The species is generally peaceful with suitable fish, but it swims quickly and becomes fairly large. Seriously Fish warns that its activity may disturb small or slow tankmates. No individual fish combinations have been entered as sufficiently supported for this guide; shared water values alone are not enough. Keep at least six of its own kind, more if the aquarium allows. Males display colour and fins to each other and females. Locality forms vary, and rainbowfish may hybridise with related forms. Keep those lines separate if you want to preserve pure stock. If considering a community aquarium, observe feeding competition, fins and shelter use.

Feeding

Melanotaenia trifasciata is an omnivore that forages mainly near the surface and in midwater. Wild foods include aquatic and terrestrial insects, algae, plant material and small invertebrates; proportions vary by habitat. Offer a varied suitable dry food as a base if the fish take it, with small frozen or live foods in rotation. The existing catalog has a complete omnivore flake as a staple option and dried daphnia only as occasional variety. Do not rely on dry food alone, and give small portions that reach the whole group. Check that less dominant fish feed too; rainbowfish can eat quickly. Good food does not replace adequate space, stable water or suitable group size.

Breeding

This species is an egg scatterer and ANGFA reports that it can spawn at intervals throughout the year. Fine-leaved plants or a spawning mop give the eggs a surface; a separate breeding tank makes collection and rearing easier. Seriously Fish describes slightly hard alkaline water, around pH 7.5 and 26.5–29 °C for a breeding setup. This is not a reason to change the main aquarium abruptly. Eggs attach to plants or a mop by fine threads. One source says adults often eat eggs, while ANGFA describes temporary territorial behaviour around the spawning site; check regularly and move eggs if needed. ANGFA reports hatching in about six to seven days depending on conditions. Fry initially need very fine food and careful water quality.

Sources & review

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

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