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This profile was written by Mary an active contributor to the site.  

Papua New Guinea


Lake Kutubu Rainbowfish

Melanotaenia Lacustris



    Melanotaenia lacustris is a popular rainbowfish in the retail community. This species is known for the brilliant turquoise color and bright yellow or orange spawning stripe that they possess. This is one of the larger growing rainbowfish species, often reaching 5 inches and over. They are a peaceful schooling fish suitable for community aquariums. However, I found mine to dominate my mixed community rainbowfish tank because of their size. This fish grows quickly and in my opinion is not suitable for aquariums less than 75 gallons.

Quick stats:

    Listed tank sizes are the minimum
    Size: 4 – 5 inches (10 - 12.7cm)
    Tank: Having kept the fish I would say 55 gallons absolute minimum based purely on experience with the fish and how big and fast they grow.
    Strata: All
    PH: 7.0 to 8.0
    Hardness: Soft. dh Range 9.0-12.0
    Temperature: 68°F to 75°F (20°-24° C)


    Order: Atheriniformes (silversides)
    Family: Melanotaeniidae (Rainbowfishes, blue eyes)
    Genera: Melanotaenia
    Species: lacustris
 Lake Kutubu from space

Common name:

    Lake Kutubu Rainbowfish, Turquoise Rainbowfish

Image gallery:
    Additional species photographs


    Badmans' Forum


    Papua New Guinea: Found only in Lake Kutubu and the Soro River, which is the only outlet stream of the lake

General Body Form:

    As with the other Melanotaenia species, the body is rounded, and the fins and tail are not remarkable in size or shape.

    Melanotaenia lacustris can display an array of different colours and patterns ranging from cobalt blue, steel blue, aquamarine through to lighter and darker shades of turquoise. When spawning, the spawning stripe typically flashes bright orange or gold. Coloration can be affected by water quality and diet.

Lake Kutubu Rainbowfish


    This is a peaceful schooling fish. They should be kept in schools of 5 or more. And should have a ratio of 2 or more females per male if possible. The ideal aquarium should include a cover of rocks, driftwood and live plants. Rainbowfish in general need nice clean water, M. lacustris is no exception. Provide them with a well filtered tank with good current and aeration and they will thrive. When water conditions are sub-optimal this fish is prone to developing columnaris, and a condition of columnaris that we call “threading.” You will see wisps of what looks like string or hair hanging off of the mouth or sides of the fish. This is a sure sign that the water conditions are sub-optimal and performing extra water changes will clear it right up.

    They need an omnivorous diet. They love live insects, live blackworms, artemia, frozen foods, and flakes. But they should be provided with a good source of vegetation, as well. They will readily nibble on hair algae in the tank and duckweed, if made available to them.
Lake Kutubu Rainbowfish

    Clear, still, and deep water of the lake.

    Spawning females produce between 100 and 200 eggs, spawning a number of times daily for several days. Eggs adhere to water plants and hatching occurs after 6-10 days, depending on temperature. Most aquarists use homemade mops for rainbowfish of all species to deposit eggs in.

    Velvet Disease 2 (Piscinoodinium sp.), Parasitic infestations (protozoa, worms, etc.)

    Home of the Rainbowfish - Lacustris
    Fisbase - Lacustris
    Rainbowfish, A Complete Pet Owner's Manual by Gunther Schmida
    Baensch Aquarium Atlas 3, Second English Edition 1998

Your comments:


Please remember that the following comments are personal experiences and may or may not apply to your setup. Use them as guide to help better understand your fish, like us all individuals will behave differently under different circumstances.


From: Tom
One of the most beautiful fish. Striking against a black back ground. Very peaceful and great fish with other rainbows and torpedo barbs. Not a picky eater and easy to care for.






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