Red rainbowfish

Overview

The red rainbowfish (Glossolepis incisus), from Lake Sentani in Papua, is one of the most striking large rainbowfishes. A dominant male is a deep, glowing brick red with a high-backed, muscular body, while females and subordinate males stay silvery-olive. Peaceful, hardy and long-lived, it makes a superb centrepiece for a big community — as long as you can meet its need for space and give it the time it takes to colour up fully.

Tank & water

This is a big, active shoaler. Give a group a minimum of 200 litres (50 gallons) with a long footprint.

• Space first: length and open swimming room matter more than anything. Cramped rainbowfish are stressed rainbowfish.
• Water: neutral to hard and slightly alkaline, pH 7.0–8.0. Very soft, acidic water is not ideal.
• Warmth and filtration: hold 24–28 °C with a heater, and use a strong filter — these are hungry fish that produce a real bioload and enjoy some current.
• Mature tank and a lid: cycle fully first, and cover the tank, as rainbows jump.

Feeding

An unfussy omnivore with a big appetite. Feed quality flakes and pellets from the fish food range as a staple, backed by frequent live and frozen foods — bloodworm, brine shrimp, daphnia — and some vegetable matter. Rich, varied feeding is what fuels the males’ colour.

Tankmates

Peaceful but large and boisterous, red rainbowfish suit spacious community tanks with robust companions: other big rainbowfishes, larger tetras and barbs, peaceful cichlids, bristlenose plecos and larger corydoras. Avoid tiny nano fish that will be swept aside at feeding time. Keep a shoal of six or more with several males for the best colour and behaviour.

Plan the setup with our best large aquarium picks and check numbers against how many fish in an aquarium.

Common mistakes to avoid

• Housing them in too small a tank
• Expecting instant red colour from young fish
• Keeping too few — a small group looks and behaves poorly
• Pairing them with tiny, timid nano fish