Lake Kutubu rainbowfish

Melanotaenia lacustris

Also known as Turquoise Rainbowfish

FreshwaterFish

Lake Kutubu rainbowfish (Melanotaenia lacustris) — Thomnight (Thomnight) · CC BY-SA 2.0 de

Care at a glance

Temperature: 68–77°F (20–25°C)
pH: 7.0–8.0
Adult size: 4.3 in (11 cm)
Minimum tank: 29 gal (110 L)
Temperament: Peaceful
Social behavior: Schooling
Swim level: Middle
Difficulty: Medium
Breeding: Hard
Rarity: Rare
Origin: New Guinea
Family: Melanotaeniidae

Overview

Lake Kutubu rainbowfish are calm, midwater schoolers best kept in a group of six or more, where males glow in the blue and turquoise the species is known for. They are peaceful and pair well with other gentle fish that enjoy the same cool, hard water. Steady conditions and a mature group bring out the deepest color, so be patient with plainer youngsters. Feed a mix of flake or pellet, frozen bloodworms, daphnia, and brine shrimp. Plant the sides and keep the center open for swimming. Aim for a tank around 110 liters or larger.

In the wild

This species is endemic to Lake Kutubu and its outflow in the highlands of Papua New Guinea, one of the country's largest and clearest lakes. The water is cool, hard, and slightly alkaline, which suits a pH of about 7 to 8 and a temperature between 20 and 25 degrees Celsius, on the cooler side for a rainbowfish. Recreate it with fine substrate, rockwork and wood, sturdy plants around the edges, and clean, well-oxygenated water with gentle movement.

Good to know

Melanotaenia lacustris belongs to Melanotaeniidae and grows to around 11 centimeters. The name lacustris means of the lake, and the species is unusual for a rainbowfish in living naturally in just one lake system. Males show the strongest blue, shifting shade with mood and light. It is a continuous egg-scatterer, laying small numbers of eggs onto fine plants and mops over weeks, with the fry left to fend for themselves, so breeding is rated hard.

Did you know

The Lake Kutubu rainbowfish can change how blue it looks from moment to moment, brightening or fading with its mood and the light. As a fish tied to one highland lake, it is listed as vulnerable in the wild.