哈氏铅笔鱼 · Blackstripe Pencilfish

Overview

Uncommon in trade, Nannostomus harrisoni may arrive mixed with Nannostomus eques. It is small, peaceful, and timid. Red pigmentation in the pelvic, anal, and tail fins of mature males provides useful sexing clues.

Distribution & habitat

The type locality is a canal near Christianburg, Guyana. The species appears restricted to the Demerara and some tributaries in eastern Guyana.

Slow tributaries, small rivers, and swampy areas provide plants, submerged wood, and leaves. Flooded forest and floodplain lakes are also used.

Aquarium setup

Allow a footprint of at least around 60 × 30 cm. Dense planting, dark substrate, and floating cover create a sheltered setting. Branches and dry leaves add structure, and fish may gather around floating plants. Microorganisms associated with leaf decomposition can supplement fry food.

Use gentle filtration, usually an air-driven sponge filter, although some current is tolerated.

Diet & feeding

Tiny invertebrates and other zooplankton form the natural diet. In captivity, combine suitable-sized preparations with daily Artemia nauplii, small water fleas, grindal worms, and similar live or frozen foods.

Behaviour & compatibility

Peaceful but retiring, it should not be housed with much larger or forceful fishes. Similar-sized peaceful characins and smaller bottom-dwelling catfishes are better candidates. Its middle-to-upper activity and lack of active fry hunting can make it useful with suitable dwarf cichlids, without guaranteeing that no fry are eaten.

Maintain at least ten where possible. Larger groups improve confidence and distribute social pressure. Unlike some relatives, males seldom spar persistently or injure one another.

Sexual dimorphism

Mature males have red in the pelvic, anal, and tail fins. Female pelvic and anal fins are more transparent, and tail color is weaker. Males are normally slimmer, while egg-filled females are noticeably fuller.

Breeding

Aquarium reproduction has succeeded but is uncommon. Occasional fry may appear in a mature planted tank. To improve yield, prepare a separate container with aged water and abundant fine wool mops or fine-leaved plants.

Bright lighting is unnecessary, and a small air-driven sponge filter can be used. After conditioning adults together, introduce a pair or one or two males with several females. Additional adults increase egg predation, and multiple males may distract one another.

Remove adults after roughly two or three days; the first fry may appear another day or two later. Begin with Paramecium or fine preparations around 5–50 μm, then introduce Artemia nauplii or microworms when the fry can manage them.

Notes

A strong middle body stripe is accompanied by a less distinct upper stripe, and an adipose fin is present. The male anal fin does not extend to the tail base as in some related species.

Oblique blotches or vertical camouflage markings appear after dark. A changed pattern when lights come on is normally part of the day-night rhythm and does not establish nocturnal activity.