What is a Pencil Fish?

A Pencil Fish is a slender, peaceful freshwater species, named for its pencil-like shape. Native to South America's slow-moving waters, these fish add a unique dynamic to aquariums with their playful behavior and schooling nature. Intrigued by their charm and ease of care? Discover how Pencil Fish could be the perfect addition to your aquatic family. What might they reveal about your aquarium's harmony?
Jason C. Chavis
Jason C. Chavis

A Pencil Fish is a freshwater fish found throughout South America. Known scientifically as Nannostomus, it is commonly used as an aquarium fish due to its coloring and shape. They are relatively small, ranging in size from only one to two inches (2.5 - 5.1 cm).

The Pencil Fish is native to most of the northern area of South America, particularly the Amazon basin. Countries such as Colombia, Venezuela, Bolivia and Brazil maintain a strong market on these types of fish. Although the Pencil Fish is traditionally found in these areas, they have been adapted to the climate of Asia as well. Today, they are found nearly worldwide due to their use in aquariums.

Nannostomusis are found throughout South America.
Nannostomusis are found throughout South America.

In the past, scientists have attempted to categorize the different types of Pencil Fish based strictly on the coloring of their bodies. This has been found to be apocryphal, as the fish are all basically identical. Today, researchers have determined that there are simply 17 distinct species which comprise the Nannostomus genus, most notably the Nannostomus beckfordi and Nannostomus harrisoni, used in trade.

Depending on the variety of Pencil Fish, the coloring and patterns vary significantly. Many have black or brown horizontal stripes with tinges of gold or silver. Others have a variety of blotches covering their bodies. The fins of the various species are usually vividly colored and can come in nearly any shade. These fins can be long or short depending on the sex and species.

While native populations of South America had known of the Pencil Fish, it wasn't added to the scientific records until 1872. Numerous scientists recorded the existence and species types through drawings and writings for years. It wasn't until 1933, however, that actual photographs of the fish were published in scientific journals. William T. Innes was the photographer, known widely for his work on taxonomy. Over the years, the different species were often mistaken for different genus types, but in 1975, they were merged into the unified genus Nannostomus.

The Pencil Fish is best kept in aquariums with temperature ranges of 72°F (about 22°C) to 82°F (about 28°C). While they can be used as general community fish, they thrive most readily when associated with other species of the same genus. Owners of these fish should feed the animals brine shrimp and algae as well as keep aquatic plants in the tanks to help with oxygen production.

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    • Nannostomusis are found throughout South America.
      By: Iryna Volina
      Nannostomusis are found throughout South America.