Lake Kutubu Rainbowfish

The Lake Kutubu Rainbowfish, scientifically known as Melanotaenia lacustris, is a stunning freshwater species that has enchanted aquarium enthusiasts with its striking appearance and captivating behavior. Native to the pristine waters of Lake Kutubu in Papua New Guinea, this rainbowfish species offers a burst of vibrant colors and engaging behavior that make it a prized addition to any freshwater aquarium. In this comprehensive guide, we will dive into the fascinating world of the Lake Kutubu Rainbowfish, covering its size, appearance, habitat, behavior, dietary preferences, and expert advice on keeping them in your home aquarium.


The Lake Kutubu Rainbowfish is a medium-sized species, growing up to 10-12 centimeters (4-5 inches) in length. Its sleek body is adorned with iridescent scales that shimmer with hues of blue, green, and yellow. Males are more vibrant and colorful than females, displaying elongated fins and intense coloration, particularly during courtship displays, where the coloration around the neck area intensifies.


Melanotaenia lacustris hails from the crystal-clear waters of Lake Kutubu in Papua New Guinea (An island North of Australia). This lake is surrounded by lush rainforests and is renowned for its unique biodiversity. Lake Kutubu is one of Papua New Guinea’s largest lakes (60 km2) and was formed when a volcano erupted and its debris blocked off a valley. Most fish found in this lake are endemic. The rainbowfish’s natural habitat includes dense vegetation, submerged logs, and rocky areas. Replicating these conditions in your aquarium is essential for their well-being.


Lake Kutubu Rainbowfish are known for their peaceful and social behavior. They are typically found in groups in the wild, and this schooling behavior continues in captivity. These fish are active swimmers and enjoy exploring their environment. They coexist well with other non-aggressive fish species in a community tank setup.


In their natural habitat, Lake Kutubu Rainbowfish are omnivores, feeding on a combination of aquatic insects, zooplankton, and plant matter. In a home aquarium, they readily accept high-quality flakes, pellets, and live/frozen foods such as brine shrimp, daphnia, and bloodworms. Including plant-based foods like spirulina flakes in their diet maintains their health and color vibrancy.

Keeping Lake Kutubu Rainbowfish at home

Creating an optimal environment for Lake Kutubu Rainbowfish requires careful attention to tank setup, water parameters, and tank mates. Here are some key considerations:

Tank size: Provide a spacious aquarium with a minimum capacity of 150 liters (40 gallons) to accommodate a small group of Lake Kutubu Rainbowfish. Larger tanks allow for better schooling behavior and territorial distribution.
Water parameters: Maintain water temperature between 20-25 °C (68-77 °F) and a pH level of 7.0-9.0. The water hardness should range from 10-20 dGH. Regular water changes of around 20% every two weeks help maintain optimal water quality.
Aquarium setup: Emulate their natural habitat by including dense vegetation, submerged logs, and rocky hiding spots. Use a sandy or fine gravel substrate to mimic their native environment.
Tank mates: Lake Kutubu Rainbowfish are peaceful and can coexist with other peaceful fish species like tetras, gouramis, and other rainbowfish. Avoid aggressive or larger fish that may stress or intimidate them.

The Lake Kutubu Rainbowfish, with its mesmerizing colors and social demeanor, is a true gem for freshwater aquarium enthusiasts. By understanding their size, appearance, habitat, behavior, and dietary requirements, you can create a thriving and visually captivating underwater world within your own home. Invest in the care of Melanotaenia lacustris, and you’ll be rewarded with a stunning display of natural beauty and the joy of witnessing their vibrant interactions in your aquarium.

Scientific nameMelanotaenia lacustris
Type of aquariumFreshwater
Size10-12 cm / 4-5 inches
RegionLake Kutubu, Papua New Guinea
Ideal tank size150 liters / 40 gallons
Ideal water temperature20-25 °C / 68-77 °F
DietOmnivorous, aquatic insects, zooplankton, plant matter
ReproductionSuccessful captive breeding has been reported under the right circumstances. Put three males to two females in a tank with soft acidic water and fine leaved plants to have success.
Life span5-8 years
SchoolingSocial, prefers living in groups

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