Tropical Fish Keeping banner

Harrison's Pencilfish (Nannostomus harrisoni)

3978 Views 0 Replies 1 Participant Last post by  TFK Team
Family: Lebiasinidae, Subfamily Pyrrhulininae

Common Name: Harrison's Pencilfish

Origin and Habitat: Endemic to the Rio Demerara basin, Guyana. Found in slow-flowing streams, swamps and flooded forest.

Compatibility/Temperament: Peaceful, very shy. Must be kept in a group, minimum 5-6 but preferably more. Like most pencilfish, males are territorially aggressive but no damage results. Cannot be kept with large or aggressive species, since it will withdraw and likely refuse to eat. Good in a species tank or with other small, peaceful fish such as other pencilfish, smaller characins and rasbora, Corydoras and other catfish that remain small.

Harrisons Pencilfish Diet

Food must be tiny as this fish has a very small mouth. Ground flakes, frozen and fresh daphnia, small worms, insect larvae, brine shrimp. The fish will continually browse plant leaves, wood, etc., picking off microscopic creatures. It feeds from the surface, but will also capture foods that sink very slowly.


Attains 4.5 cm (almost 2.5 inches) and is very slender.

Minimum Tank Suggestion

10 gallon for a small group alone, but better in a 24 inch tank (15+ gallons).

Water parameters for Harrisons Pencilfish

Soft (< 5 dGH), acidic (pH 5.5 to 7), temperature 23-28C/74-82F. Fish will be wild caught and will not do well in basic or harder water.


This pencilfish is not common in the hobby, and within the genus it is somewhat different from all other species known to date. It is the largest but quite slender, rather torpedo shaped. It is benthopelagic (living near the substrate, mid-water and higher) but frequents the surface among floating plants. It continually browses the finest plant leaves, wood and rock for zooplankton and other minuscule particles of food; aside from this, it swims horizontally, not angled like the similarily shaped N. eques and N. unifasciatus.

The aquarium should be well planted, with a dark substrate and subdued lighting. Floating plants are mandatory. The filter current must be very low, as this fish occurs in very still waters (see under Origin). Twisted branches and chunks of wood are ideal. Dried leaves can be placed on the substrate, and the fish will consume infusoria from these.

Males are a bit thinner than females, and more brightly coloured. Like other pencilfishes, this one is an egg scatterer and spawns in plant thickets; Cabomba, similar stem plants and Java Moss are suitable. Eggs will be readily eaten if not separated from the fish.

This species does not possess an adipose fin. In common with all pencilfish, the fish has a small terminal mouth that is always open, and (except for N. espei) a diurnal colour pattern. During darkness, the horizontal line breaks up into a series of dashes. This has been observed in blind fish, showing that it is an automatic response and not controlled by the fish.

Originally described in 1909 by C.H. Eigenmann as Poecilobrycon harrisoni, it was moved into Nannostomus by Weitzman and Cobb (1975).

All pencilfish are found in the tribe Nannostomini in the subfamily Pyrrhulininae. Three different genera (Nannostomus, Nannobrycon and Poecilobrycon) were used at various times until Weitzman & Cobb (1975) placed all species in the single genus, Nannostomus, erected by Gunther in 1872 with N. beckfordi as the type species; Gery (1977) separated them into two genera, Nannostomus and Nannobrycon, largely on the basis of the swimming position. Weitzman & Weitzman in Reis et al. (2003) reassigned the species into the single genus Nannostomus which now includes all described pencilfish. The genus name Nannostomus comes from the Greek meaning "small mouth."


Gery, Jacques (1977) Characoids of the World, TFH Books.

Reis, R.E., S.O. Kullander & C.J. Ferraris Jr. (2003), Check list of the freshwater fishes of South and Central America.

Weitzman, Stanley H. (1966), "Review of South American Characid Fishes of Subtribe Nannostomina," Proceedings of the United States National Museum (Smithsonian Institution), Volume 119, Number 3538.

Weitzman, Stanley H. & J.S. Cobb (1975), "A revision of the South American fishes of the genus Nannostomus Gunther (family Lebiasinidae)," Smithsonian Contributions to Zoology No. 186.

Contributing Members

The following members have contributed to this profile: Byron


See less See more
1 - 1 of 1 Posts
1 - 1 of 1 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.