One-lined pencilfish are popular in aquaria due to their size, colour display and swimming posture, and were introduced in this way to Trinidad.
One-lined pencilfish and its scientific name Nannostomus unifasciatus are popular in aquaria and are used as ornamental fishery resource by riverine communities from central Amazonia. They gain popularity due to their size, colour display and swimming posture, and were introduced in this way to Trinidad.
ONE-LINED PENCILFISH DESCRIPTION:
It is a small fish found in flooded forests of the Rio Negro Floodplain in central Amazonia, Brazil. They can be found in forest streams, swamp areas, rivers, tributaries and live up to 5 years. Adults grow to an average length of 4 cm and maximum of 7 cm.
These fish are elongated fish with a pale to olive brown back and have a very well developed primary horizontal stripe with a long black stripe which runs laterally down the central length of its body and onto its indented caudal fin. Secondary and tertiary horizontal stripes are absent with 2 silver metallic bands border the single black stripe. The color of the caudal fin is variable and is dependent on the geographic population of the fish.
This fish closely resembles Nannostomus eques (diptail pencilfish or brown pencilfish) but can be easily distinguished by the more defined dark lateral stripe and the absence of dark spots in the scales and normally possesses an ocellus in the upper caudal-fin lobe.
Males and females have different shape and colors with respect to their body and fins. The males are narrower-bodied and have elongated anal fins and the tips of the ventral and anal fins are brighter and more outstanding compared females. Males establish and defend small territories but rarely cause harm to each other. They are sociable in groups as males are friendly towards females.
ONE-LINED PENCILFISH CARE:
Nannostomus unifasciatus thrive in water that is slightly acidic with pH ranges from 4.0-6.5 and temperature ranges from 23-28 °C with minimum tank of 10 gallons. The flow from the filter should be very subdued; in small tanks a single sponge filter is ideal, and in larger aquaria ensure there is minimal flow plus some very still areas.
They should ideally be kept in a heavily-planted set-up, preferably with a dark substrate and some patches of floating vegetation around which the fish will tend to congregate, bodies angled towards the surface. They are timid fish which hide in aquatic vegetation and leaf litter, so driftwood branches and dried leaf litter can also be added.
They are social fish which usually exist in groups of 10 or more of the same kind. The greater the size of the school of fish, the more stable the community as rivalries occur less. In a community it’s best kept with similarly-sized, peaceful characids and smaller callichthyid or loricariid catfishes.
In their natural habitat, they are omnivore, micro-predator which feeds on periphyton, insects, worms and small crustaceans. In the aquarium it will accept dried foods of a suitable size but should also be offered daily meals of small live and frozen fare such as Artemia nauplii, Moina, grindal worm, etc. They tends to congregate in the mid to lower reaches.
ONE-LINED PENCILFISH BREEDING:
These fish are egg-layers; soft, acidic waters which are fairly warm induce spawning. When water conditions are unfavorable, the colors of this fish may fade. The males flash their brightly coloured displays as part of courtship then adult females scatter their eggs among plants and the males discharge their sperm into open water as fertilization is external. The pair select a leaf and the eggs are deposited on the underside.
After spawning, the parent fish are not involved with the eggs anymore. The eggs can number up to a hundred, and hatch within 36 hours. The larvae first feed on the yolk sac and later as they grow, start feeding on periphyton. The larvae first cling to surfaces early on while absorbing the yolk sac, but within five days the fry are able to swim.
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