Turquoise Rainbowfish ~ Melanotaenia lacustris

The Turquoise Rainbowfish is one of the most striking members of the rainbowfish family, known for its vivid blue-green body that glows like polished gemstone under aquarium lighting. Native to Lake Kutubu and its connecting waters in Papua New Guinea, this species is admired for its peaceful temperament, deep-bodied profile, and shimmering color gradients that shift from teal and silver to turquoise with maturity. Its energetic schooling behavior and bold presence make it a standout centerpiece fish in medium to large freshwater aquariums.

• Size: 4.5-5 inches

• Lifespan: 5-10 years

• Temperament: Peaceful, active

• Group/Solitary: Best kept in groups of 6+

• Food: Omnivorous, high-quality flakes or pellets, spirulina, live/frozen foods such as bloodworms, brine shrimp, and daphnia

• Water Requirements: 75-82°F, pH 7.0-8.0, moderate hardness

Turquoise Rainbowfish thrive in spacious, well-oxygenated aquariums with plenty of horizontal swimming room and dense vegetation around the edges. Their coloration becomes dramatically more vibrant when kept in groups and provided a varied, high-quality diet. Stable, high-clarity water with moderate flow mimics their native lake environment and helps maintain bold hues and active behavior. They are excellent community fish when paired with other peaceful, similarly sized species that can match their speed and activity level. Regular water changes are key to keeping this species in peak condition.

In the wild, Turquoise Rainbowfish inhabit the pristine waters of Lake Kutubu and its connected streams, a unique ecosystem known for exceptional water clarity and rich submerged plant life. The lake’s mineral composition and steady daylight penetration contribute to the fish’s intense metallic coloration, which helps individuals communicate within large schools while remaining less visible to predators against bright, reflective backgrounds.

Fun Fact: The turquoise coloration of this species can shift throughout the day, appearing brighter during courtship or when males display dominance, creating a shimmering effect as the entire school moves through the water.