Turquoise Rainbowfish

Also known as: Melanotaenia lacustris

The Turquoise Rainbowfish (Melanotaenia lacustris) is a vibrant freshwater species native to Lake Kutubu in Papua New Guinea. The Turquoise Rainbowfish originates from Lake Kutubu and surrounding tributaries in Papua New Guinea, reaches Adult size: 10-12 cm in captivity, typically lives 5-8 years, and is kept at 24-28°C (75-82°F). Individual fish vary, so treat this as a general guide rather than a guarantee.

Species at a glance

Origin: Lake Kutubu and surrounding tributaries in Papua New Guinea
Adult size: Adult size: 10-12 cm (4-5 inches)
Life span: 5-8 years
Temperament: Peaceful and active schooling fish; best kept in groups of 6 or more
Tank size: Minimum 114 liters (30 gallons) for a small group; 189 liters (50 gallons) recommended for optimal schooling behavior
Water temp: 24-28°C (75-82°F)
pH range: pH 7.0-8.0
Diet: Omnivorous; accepts high-quality flakes, micro pellets, and live/frozen foods such as brine shrimp, daphnia, and bloodworms; supplement with vegetable matter like spirulina
Other names: Melanotaenia lacustris

About the Turquoise Rainbowfish

The Turquoise Rainbowfish (Melanotaenia lacustris) is a vibrant freshwater species native to Lake Kutubu in Papua New Guinea. Males display striking iridescent turquoise-blue coloration along the flanks, especially during breeding, while females are more subdued with silvery-green hues. They are active swimmers that inhabit the upper and middle water columns, requiring open space for schooling. This species is valued in the aquarium trade for its peaceful nature and stunning visual appeal in community tanks.

Lifespan and health

With proper care, Turquoise Rainbowfish typically live 5-8 years in captivity, though exceptional individuals may reach up to 10 years under optimal conditions. Longevity is strongly influenced by diet variety, water stability, and low stress levels; fish kept in groups of 8-10 with ample space and clean water show significantly better long-term health and color retention. Breeding activity can slightly shorten male lifespan due to energy expenditure, so providing rest periods and balanced nutrition is key. Common health issues include ich (white spot disease) during temperature fluctuations or poor acclimation, preventable by maintaining stable temps and quarantining new arrivals. Fin rot may occur in overcrowded or dirty tanks, signaled by frayed edges; treat with improved water quality and antibacterial agents if needed. Internal parasites are rare but possible if live food is sourced unsafely—always use cultured or frozen alternatives. Regular observation for lethargy, loss of color, or clamped fins allows early intervention, and a well-maintained tank rarely sees serious disease outbreaks.

Overview

Care and tank setup

Tank setup should include a sandy or fine gravel substrate with dense planting along the sides and background using hardy plants like Vallisneria, Java fern, or Anubias to provide shelter while leaving open swimming space in the center. Driftwood and rock arrangements can be added for natural aesthetics, but avoid overcrowding the midwater zone. A tight-fitting lid is essential as these fish are known jumpers, especially when startled or during feeding frenzies. Water conditions must be stable and well-oxygenated; perform 25% weekly water changes to maintain low nitrate levels (<20 ppm). Use a filtration system rated for at least twice the tank volume to ensure adequate flow and waste processing, mimicking the clear, flowing streams of their native habitat. Maintain consistent parameters: temperature 24-28°C (75-82°F), pH 7.0-8.0, and hardness between 10-20 dGH. Avoid sudden fluctuations, as Turquoise Rainbowfish are sensitive to poor water quality. Feed small amounts 2-3 times daily, offering only what they can consume within 2-3 minutes to prevent overfeeding and water degradation. Rotate diet regularly: base diet of high-protein flakes or micro pellets supplemented 3-4 times weekly with live or frozen foods like brine shrimp or daphnia. Include vegetable-based foods (e.g., spirulina flakes or blanched zucchini) 1-2 times weekly to support digestive health and enhance coloration. Remove uneaten food promptly to maintain water quality.

Adding a Turquoise Rainbowfish? Research the species’ adult size and temperament carefully, quarantine new fish before introducing them to your tank, and buy from reputable aquarium stores or breeders.

Breed information on this page is based on the Wikipedia article on the Turquoise Rainbowfish, supplemented with additional research. Reviewed for accuracy.