管口铅笔鲤 · Hockeystick Pencilfish

Overview

The characteristic head-up, tail-down swimming angle of Nannostomus eques is normal behavior, often seen around floating plants. Peaceful and strongly social, it suits a densely sheltered aquarium with gentle filtration.

Distribution & habitat

Records span the central and upper Amazon in Brazil, Peru, and Colombia, the Orinoco system in Venezuela and Colombia, and several Guyanese rivers.

It inhabits slow tributaries, small rivers, swamps, flooded forest, and floodplain lakes, especially in blackwater regions rich in plants, wood, and leaves. One lower-Atabapo observation in Colombia found fish in shallow, acidic, tea-colored water among flooded terrestrial vegetation.

Genetic work on similar-looking Negro River populations suggests separate evolutionary units, raising the possibility of hidden species within the present name. Locality information is therefore useful.

Aquarium setup

Provide a footprint of at least approximately 60 × 30 cm. Dense planting, dark substrate, and floating cover create suitable shelter. Leave usable space around floating plants, where fish gather at an upward angle. Branches and dry leaves add cover, with decomposition supporting microorganisms that can supplement fry food.

Gentle filtration is appropriate. An air-driven sponge filter is usually enough, although some current is tolerated.

Diet & feeding

Tiny invertebrates and other zooplankton form the natural diet. Captive fish accept appropriate-sized preparations, supplemented daily with small live or frozen foods such as Artemia nauplii, small water fleas, and grindal worms.

Behaviour & compatibility

Its peaceful but timid nature makes much larger or forceful companions unsuitable. Similar-sized peaceful characins and smaller bottom-dwelling catfishes are better candidates. Middle-to-upper activity and absence of active fry hunting make it useful as a dither fish for some dwarf cichlids, without guaranteeing that no fry will ever be eaten.

Keep at least ten where possible. Larger groups are more confident and behave more naturally. Unlike some other pencilfishes, rival males seldom spar or injure one another.

Sexual dimorphism

Adult males are more colorful and usually slimmer, with an enlarged anal fin. Females tend to be fuller-bodied.

Breeding

Aquarium breeding has succeeded, although infrequently. Occasional fry may survive in a mature planted setup, while a separate container provides more control. Condition adults together and prepare breeding containers with aged water and broad-leaved plants.

Unlike most relatives, eggs are placed in batches beneath leaves. Introduce a pair, or one or two males with several females. More adults increase the risk because fish eat eggs they find. Once eggs are visible, remove the adults or transfer the plant to a separate hatching tank.

Hatchlings may appear after about 24–36 hours, with most swimming freely by day five or six. Start them on Paramecium or fine foods around 5–50 μm, then add Artemia nauplii or microworms when the fry can swallow them.

Notes

The relative Nannostomus unifasciatus also swims obliquely, so posture alone does not establish identity. A cryptic barred pattern may replace the daytime colors after dark; this normal rhythm explains changes noticed when lights are switched on.

Older records may use Poeciliobrycon or Nannobrycon. Assess overall markings, locality, and morphology instead of relying on one trade name.