is a genus of fish belonging to the Lebiasinidae family of Characins,
known as Pencilfish. All species are slender, pencil-shaped fish ranging
in size from under 1" to approximately 2" in length. All swim
in a horizontal attitude except Nannostomus unifasciatus and Nannostomus
eques, which assume an oblique, 'snout-up' posture. In some species,
males are more brilliantly colored, especially with regard to color
present in the fins. However, a reliable indicator of gender for most
of the species rests in the anal fin of adult males which is enlarged
and elongated and/or the anal fin of males is more colorful. The genus
has a vast distribution in South America, from Colombia, Venezuela and
the Guyanas in the north, to the southern Amazon basin and Bolivia in
the south, to Peru in the west and Belem, Brazil in the east.
In their natural enviornment most Pencilfish live in soft and acidic
waters (pH 5.5-6.8), low nitrate levels, and temperature ranging from
25 to 28¢X C. Pencilfish do best in a well-planted aquarium with moderate
lighting using dark substrate to display their coloration. Best kept
in a group comprising a minimum of six individuals of the same species.
Good tankmates are other Nannostomus species, peaceful tetras, rasboras,
corydoras, plecos, and more. If kept in a thickly planted single-species
aquarium with the above water parameters, most species will spawn, eggs
will not be eaten, and the fry will be found among the floating plants.
Baby brine shrimp, live or frozen, and other small-sized foods are required
for both fry and adults. In most species the males will establish small
territories and defend them. Their defensive actions are usually harmless.
Once acclimated to the aquarium, and provided with conditions to their
liking, Nannostomus are hardy and often live for five or more years.