Emerald Rainbowfish Care Guide - Aquarium Setup, Diet & Breeding

Emerald Rainbowfish are robust, deep-bodied members of the rainbowfish family, prized for their shimmering scales and lively presence. Mature males develop especially intense coloration, with metallic green, bronze and red tones that can change dramatically as they display or become excited. Despite the common name used here, Glossolepis incisus is also widely known in the aquarium trade as the Red Rainbowfish, reflecting the strong red coloration often seen in adult males.

These are active, confident fish that spend much of their time in open water. Males court females with extended fins and vivid colour, often positioning themselves side-on to show their reflective flanks. Their constant movement and bold personality make them an eye-catching feature fish for a spacious community aquarium.

In the wild, they inhabit Lake Sentani, a large tropical lake surrounded by forested and mountainous terrain. The lake contains shallow margins, vegetated areas and open stretches of water, providing a mixture of cover and room for swimming. Wild populations have faced pressure from habitat change and introduced species, making responsible sourcing particularly important.

Emerald Rainbowfish are peaceful when kept with appropriately sized companions, although their energetic swimming can overwhelm very timid or slow-moving fish. They are best appreciated as a sizeable group, where natural social behaviour and the males' colourful displays are most apparent.

Glossolepis incisus is native to Lake Sentani and connected waterways near Jayapura in Papua, Indonesia. It comes from the freshwater habitats of western New Guinea in Oceania.

A group should have at least 200 litres, with a recommended footprint of approximately 120 x 45 cm; a longer aquarium is preferable because these are powerful, active swimmers. Use efficient filtration and good surface movement to maintain high oxygen levels, while avoiding an excessively turbulent current. Arrange plants densely around the sides and rear, leaving a broad open swimming area, and include some floating cover to soften the lighting. A dark, fine gravel or sand substrate, driftwood and smooth rocks create an attractive natural-style setting without obstructing their swimming space.

Males can reach about 15 cm (5.9 inches) in total length, while females are usually smaller at around 10 cm (3.9 inches).

Emerald Rainbowfish are omnivores and should receive a varied diet of quality flakes, small pellets and granules, supplemented with frozen or live foods such as bloodworm, daphnia, mosquito larvae and brine shrimp. Regular vegetable-based foods, including spirulina-rich flakes or pellets, help provide balance. Offer modest portions once or twice daily, ensuring all food is eaten promptly.

Emerald Rainbowfish suit peaceful, similarly sized community fish that enjoy warm, well-oxygenated water. Suitable companions include other appropriately sized rainbowfish, larger peaceful tetras, danios, peaceful barbs, Corydoras, larger non-aggressive loaches and peaceful suckermouth catfish. Avoid housing them with fin-nipping species, highly aggressive cichlids or delicate, slow-moving fish that may be intimidated by their activity. Smaller fish may be swallowed by large adults, particularly if they fit comfortably into the rainbowfish's mouth.

Emerald Rainbowfish are egg scatterers that readily spawn in mature aquariums. Provide fine-leaved plants or a spawning mop, where females can deposit adhesive eggs while males display nearby. Move the mop or eggs to a separate, gently filtered nursery to prevent the adults from eating them. Eggs generally hatch in around a week, and the tiny fry can be raised initially on infusoria or other suitably fine foods before progressing to newly hatched brine shrimp.

Males are larger and develop much stronger metallic colouring, often showing red, bronze and green across the body with extended dorsal and anal fins. Females are smaller, slimmer and generally silvery olive or less intensely coloured, with shorter fins.