Australian Rainbowfish (Melanotaenia nigrans)

Overview

The Australian Rainbowfish (Melanotaenia nigrans) is a peaceful, active rainbowfish from northern Australia, also known as the Black-banded Rainbowfish. It is sold in the trade as Australian Rainbow, but the scientific name is the useful anchor here because it separates this fish from other Australian rainbowfish sold under similar common names. Expect a slender, lively fish with a dark mid-lateral band, soft lavender-silver sheen, warm yellow to orange tones on mature fish and constant shoaling movement through the middle of the aquarium.

This listing covers the current Shopify product with two size options: 4.5-5.5 cm under SKU 5044 and >6 cm under SKU 5045. The product page keeps the exact Petra source photo alongside the existing aquarium lifestyle images, so you can compare the real supplied fish shape and markings with the richer planted-tank presentation. The species is hardy once settled, but it is still a fast-moving shoaler rather than a single centrepiece fish, so it looks and behaves best in a proper group.

Quick Facts

• Scientific name: Melanotaenia nigrans
• Common/trade names: Australian Rainbowfish, Australian Rainbow, Black-banded Rainbowfish
• Adult size: commonly around 6-8.5 cm, with larger males reported up to about 10 cm total length
• Temperament: peaceful, active and best kept as a shoal
• Care level: easy to moderate, mainly because it needs space and stable water
• Best aquarium: planted community tank with open swimming room
• Suggested group: 6 or more, with mixed sexes if available for better colour and confidence
• Temperature guide: 23-28°C for a tropical community setup
• pH guide: slightly acidic to neutral, around 5.5-7.0
• Diet: omnivore; quality flakes or micro-pellets plus small frozen/live foods and some plant matter

Appearance

Melanotaenia nigrans is more elegant than loud. The body is relatively slender for a rainbowfish, with a bold black band running along the flank and iridescent silver to lavender tones above it. Mature males can show stronger fin colour, a brighter head area and a fuller body shape, while females are usually slimmer and softer in colour. The exact colour varies by population, sex, age, stress level and aquarium condition, which is why settled groups often improve noticeably after a few weeks in a calm planted tank.

Natural Habitat

This species is endemic to northern Australia, with isolated populations across the Kimberley region, the Northern Territory, Groote Eylandt, Cape York and nearby island systems. Wild fish are associated with slow-flowing clear streams, billabongs, lily lagoons, swamps, vegetated backwaters and the margins of larger waterways. They are usually found around submerged plants, logs, branches and shoreline vegetation, which explains why they appreciate cover nearby while still needing open water for cruising.

Aquarium Setup

Use a mature aquarium of at least 100 litres for a small group, with more length and volume preferred if you plan to keep a larger shoal. Plant the sides and rear of the tank, then leave the front and middle open for swimming. Driftwood, smooth stones and leaf-litter-style cover suit the species well, but avoid a cluttered layout that blocks movement. A dark substrate can help the black band and warm fin tones stand out. Good filtration, gentle to moderate flow and a secure lid are sensible because rainbowfish are active and can startle.

Water Parameters

For normal home aquarium care, aim for 23-28°C and a pH around 5.5-7.0. Keep ammonia and nitrite at zero and manage nitrate with regular water changes. The species is recorded from a range of northern Australian freshwater habitats, so do not make sudden adjustments trying to force a number. Slow acclimation, clean water and consistency are the real priorities. If your local water is very hard or alkaline, ask us before mixing this species with more demanding soft-water fish.

Feeding

Australian Rainbowfish are omnivores. Use a quality flake or small floating micro-pellet as the daily base, then rotate in daphnia, brine shrimp, mosquito larvae, finely chopped frozen foods and occasional vegetable-based foods such as spirulina flake. Small meals once or twice a day are better than heavy feeding. A varied diet helps colour, body condition and breeding display without polluting the aquarium.

Behaviour and Tank Mates

This is a peaceful community fish, but it is not a slow, shy species. Keep it with similarly peaceful fish that enjoy active midwater movement: other compatible rainbowfish, danios, larger rasboras, peaceful barbs, Corydoras, bristlenose plecos and robust community tetras all make sense when water requirements overlap. Avoid fin-nippers, aggressive cichlids, very tiny fry-sized tank mates and long-finned fish that may be stressed by fast shoaling movement.

Breeding Notes

Melanotaenia nigrans is an egg-scattering rainbowfish. In planted aquariums, pairs may deposit adhesive eggs among fine-leaved plants, moss or spawning mops, often a few at a time over repeated sessions. Adults may eat eggs, so dedicated breeding setups usually remove the mop or plants to a separate hatching tank. Fry are small and need suitable first foods before moving to newly hatched brine shrimp or fine prepared fry food.

Delivery and Guarantee

Every order is packed for live-fish transport and sent with a licensed live-animal courier. Your order is covered by our Live Arrival Guarantee, and first-time customers can use WELCOME10 where the promotion is available. We never remove the real source context from listings: this page keeps the exact Petra source image and the existing visual media so you can judge the fish with more confidence before ordering online in the UK.