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. Size
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. Description
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
) 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
, 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." References:
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