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Nannostomus marginatus - Dwarf Pencilfish


  • Nannostomus marginatus - Dwarf Pencilfish

    Photo thanks to japes

    Scientific name: Nannostomus marginatus
    Common name: Dwarf Pencilfish
    AKA: Nannostomus marginatus picturatus (previously thought to be a seperate sub-species of N. marginatus).

    Country of origin: South America - Peru, Brazil, Columbia, Guyana

    pH: 4.0 - 7.0
    Temperature: 22 - 28c
    Hardness: 18 - 179 ppm
    Water flow: low - standard
    Oxygenation: standard

    Maximum size: 2.5cm

    Diet: Live, frozen, flake & pellet food of a siutable (very small) size - they are micropredators. They will benefit from daily live food.

    Males: slimmer

    They are an egg scatterer, and if provided with a mop or sufficient moss or plants, they can lay eggs, however they need to be kept from them by a division in the tank, or removal of the eggs or fish. They will predate on both their own eggs and fry.

    Tank companions: They are probably the best pencilfish with shrimps, although they will still hunt shrimplets.

    Other microfish are suitable tankmates, such as bororas; danios; chocolate, liquorice & sparkling gouramis; green neon & ember tetras; male endlers and royal whiptails, although they are very shy, so a species only tank is preferable. They live in their natural habitat with apistogramma species. Despite their continual non-stop hunting of shrimplets, I have never observed them to display any aggression toward or interest in other fish as prey.

    They should be kept in a group of 10+, which will help to spread aggression, although they rarely hurt each other.

    They swim at the middle to top of the tank.

    Mimimum tank size is 1.5ft for a small group.

    They prefer a dark substrate, heavily planted, with blackwater from decaying leaves (Indian Almond Leaves are ideal) and floating plants.

    They require a mature tank - do not add them immediately after setting up a new tank.

    Their colour will probably fade when the lights are off, and return gradually as the lights come on. They can have a diagonal bar pattern after lights off.

    Confused with:
    Nannostomus marginatus has some colour variations, depending on locality - from a mustard yellow to buff, the buff varieties can have a short or longer red line above the central black line or blending into it respectively.

    There are 19 species in the genus:

    Nannostomus anduzei
    Nannostomus beckfordi - Gold line/ Beckford's/ Golden/Brown pencilfish
    Nannostomus bifasciatus - Two-lined/whiteside pencilfish
    Nannostomus britskii - Spotstripe pencilfish
    Nannostomus digrammus - Twostripe pencilfish
    Nannostomus eques - Honeystick/Brown/Rocket/Brown-tailed/Diptail/Tubemouth pencilfish
    Nannostomus espei - Espe's/Barred pencilfish
    Nannostomus grandis
    Nannostomus harrisoni - Harrison's/blackstripe pencilfish
    Nannostomus limatus - Elegant pencilfish
    Nannostomus marginatus - Dwarf pencilfish
    Nannostomus marilynae - Marilyn's/greenstripe pencilfish
    Nannostomus minimus - Least pencilfish
    Nannostomus mortenthaleri - Coral-red pencilfish
    Nannostomus nigrotaeniatus
    Nannostomus nitidus - Shining pencilfish
    Nannostomus rubrocaudatus - Purple pencilfish
    Nannostomus trifasciatus - Threestripe/Three-lined pencilfish
    Nannostomus unifasciatus - Oneline pencilfish

    All Nannostomus spp. are legal imports to Australia as of 20/10/2013:

    The IUCN Red List reports Nannostomus marginatus as a species which has not yet been assessed at 21/10/2013:

    It is very important not to release any aquarium specimens into our waterways. Any that are not sold or re-homed/ given away, can often be re-sold to aquarium stores. If they are homed in ponds, care should be taken that they cannot escape in run-off into our waterways. Even if fish are native & local they should not be moved from one waterway to another, as this can transfer disease. If they are not local fish, they can both spread disease and either out-compete or eat local fish, shrimp & plants, causing their demise.

    They are a good fish for people with some experience (beginners +1).

    Relevant threads:
    Video of dwarf pencilfish:


    Video, keeping/treating with tea-tree & other advice:

    Video of males sparring, keeping with shrimp:

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