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



Melanotaenia praecox

Melanotaenia Praecox


    Melanotaenia Praecox are one of the most common and most stunning of the rainbowfish family. Unlike their Melanotaenia brethren this fish does not feature prominent stripes, but has a brilliant blue sheen. They are easy to sex with the males having bright red fins and the females having fins ranging in color from yellow to light orange. They look best in a tank with some shade provided from a cover of floating plants along with a dark substrate and background. They are a peaceful schooling fish suitable for community aquariums.
Quick stats:

    Listed tank sizes are the minimum
    Size: Average adult size: 2" (6cm)
    Tank: Min. Tank requirements: 32" inches in length
    Strata: Bottom, middle, top
    PH: PH recommendation 6.5 to 7.5
    Hardness: Medium, 8.0 - 18.0 dGH (will adapt to a range of specifications)
    Temperature: 72°F to 82°F (22°-28° C)


    Order: Atheriniformes (silversides)
    Family: Melanotaeniidae (Rainbowfishes, blue eyes)
    Genera: Melanotaenia
    Species: praecox

Common name:

    Dwarf Neon Rainbowfish , Neon Rainbowfish, Praecox
Melanotaenia praecox

Image gallery:
    Additional species photographs


    Badmans' Forum


    Indonesia: In small swift flowing jungle streams in the middle sections of the Mamberamo River system in northern Irian Jaya

General Body Form:

    As with the other Melanotaenia species, the body is rounder, and the fins and tail are short and unremarkable in size or shape.


    Light colored body with bright blue sheen. Males have red fins. Females have yellow to light orange fins. The males breeding stripe from top of nose to dorsal fin flashes yellow during displays.


    Melanotaenia praecox
    Melanotaenia praecox



    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. They prefer softer, slightly acidic water but will acclimate well into any ph within the average range.

    Rainbowfish in general need nice clean water, M. praecox 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.

    M. Praecox is found in clear, swift flowing streams and swampy habitats usually around sub-surface vegetation, submerged logs, or branches.


    M.Praecox is a substratum egg layer. Eggs adhere to the roots of floating vegetation , or in the leaves of fine leafed plants near the water’s surface. If using a mop breeding technique in the home aquarium, eggs look for the eggs high in the mop.

    Melanotaenia praecox
    Melanotaenia praecox
    Praecox fry showing color at about 7mm and 6 weeks.


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: Vij
I had 2 of these in my 35 gallon planted tank. I bought them when they were about an inch long, at that time they were not that colourful, used to feed them live tubifex worms, they got double their size in no time. The male used to have a yellow strip running at his back when they used to play together (probably luring the female), man this is a sight to watch the colours at their brightest at that time. They are very good community fish, they never bully any other fish in the tank.






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