Turquoise Rainbow (Melanotaenia lacustris)

The Turquoise Rainbowfish (Melanotaenia lacustris), also known as the Lake Kutubu Rainbowfish, is one of the most brilliantly colored freshwater fish in the world. Endemic to Lake Kutubu in the Southern Highlands of Papua New Guinea, males display a dazzling electric turquoise-blue dorsal coloration that transitions to silver-blue on the flanks and yellow-green on the ventral surface — a color combination that is truly unique among aquarium fish.

This large rainbowfish grows to about 12 cm and is an active, surface-to-mid-water schooling species. Like all melanotaeniids, it displays its most vivid coloration in the morning and during courtship displays when males compete for female attention. Keeping multiple males together in a large tank with appropriate females produces spectacular behavioral displays.

The Turquoise Rainbowfish comes from a highland lake environment with clear, moderately alkaline water. It requires neutral to slightly alkaline, moderately hard water, unlike many other rainbowfish that prefer slightly acidic conditions. Good oxygenation and clean water are important.

This species is peaceful with other fish and an excellent centerpiece species for large community aquariums. Its extraordinary electric coloration makes it a highlight of any aquarium display.

Water Parameters: pH 7.0–8.0, temperature 22–26°C, GH 10–20, KH 5–12. Moderately alkaline, hard water from its highland lake origin. High dissolved oxygen, clean water, and regular water changes are essential. Avoid very acidic or soft water.

Tank Setup: Minimum 200 liters for a group of 6. Open swimming space in the middle with dense planting along the sides and back. Hardy plants like Vallisneria and Sagittaria are appropriate. Moderate to strong filtration with good oxygenation. Tight-fitting lid — active jumpers.

Feeding: Omnivores with a preference for some plant matter. Offer quality flake food, spirulina flakes, medium pellets, frozen bloodworm, brine shrimp, and daphnia. Feed twice daily. Varied diet maintains their extraordinary blue coloration.

Tankmates: Compatible with other rainbowfish, larger tetras, barbs, and peaceful cichlids that tolerate alkaline water. Avoid soft-water species. Males display vigorously to each other — keep at least 3 males together with more females.

Health: Hardy in appropriate alkaline, oxygenated conditions. Sensitive to acidic water and low oxygen. Weekly water changes of 30% maintain the clean conditions they require. Watch for ich and bacterial infections.