Turquoise Rainbowfish

Melanotaenia lacustris

Common names: Turquoise Rainbowfish, Lake Kutubu Rainbowfish

Average Adult Size: 4-4.9in

Average selling size: Unsexed- ~1.5"-2"

XL: ~4"

A breathtaking freshwater rainbowfish endemic to the pristine highland waters of Lake Kutubu and its outlet, the Soro River, in the Kikori River drainage of Papua New Guinea. Prized in the aquarium hobby for its brilliant metallic blue to turquoise coloration and active, peaceful schooling behavior.

Key Features

• Maximum Size: 10.0 cm / ~4 inches SL (typically reaching 4–4.5 inches total length).
• Appearance: Sleek, fusiform (torpedo-shaped) body built for active swimming. Mature males develop intense cobalt blue to turquoise hues on the upper body with subtle reddish-orange accents in the fins; females are slimmer with softer silvery-blue to pale turquoise tones. Under good lighting, the scales show a shimmering metallic flash.
• Fin Details: Dorsal spines 5–7, dorsal soft rays 11–14; anal spines 1, anal soft rays 17–21.

Aquarium Care

• Tank Size: Minimum 40–55 gallons for a small school (6 or more recommended for best coloration and natural behavior).
• Water Parameters: Tropical freshwater; 72–82°F (22–28°C), pH 7.0–8.0, moderate to hard water (dH 9–12).
• Diet: Omnivorous — accepts high-quality flakes, pellets, frozen, and live foods. A varied diet with vegetable supplements helps maintain vibrant colors.
• Behavior: Peaceful, active mid-to-upper water column schooling fish. Excellent for peaceful community tanks with similarly sized, non-aggressive companions. Provide open swimming space, some plants or driftwood, and a tight-fitting lid as they are strong jumpers.

IUCN Satus: Listed as Endangered (EN) by the IUCN due to its extremely limited natural range. A perfect choice for dedicated aquarists who want shimmering turquoise color, lively activity, and a conversation-starting rarity in their planted or community aquarium.

Bring brilliant turquoise shimmer and elegance to your tank with the beautiful Lake Kutubu Rainbowfish!