Nannostomus anduzei

Overview

The minute pencilfish Nannostomus anduzei has intensely red areas around the male anal fin and tail base. Its shy, peaceful character favors a planted species aquarium or equally tiny, unassertive companions rather than a busy community.

Distribution & habitat

Confirmed collections come from the upper Orinoco in Venezuela and the Ererê drainage in Amazonas, Brazil, a tributary system of the middle Negro. The distance between them suggests undiscovered populations but does not confirm occurrence throughout the intervening area.

The Venezuelan type area includes a shallow forest stream connected to a lagoon. Clear, slow stream water flows over white sand, roots, and leaves; the lagoon is muddier and turbid, with emergent and floating plants. Fish were collected among vegetation in slow water influenced by the stream, not in the surrounding acidic blackwater habitats. The Brazilian population, however, came from blackwater and had longer male anal fins. One collection environment should therefore not be treated as universal.

Aquarium setup

Dense planting, a dark substrate, floating cover, and fine branches interrupt sight lines and reduce nervousness. Dried leaves encourage microbial growth that can provide supplementary food for fry.

Keep filtration gentle. An air-driven sponge is usually adequate, without forcing these small fish to swim continuously against strong flow.

Diet & feeding

Wild fish take minute invertebrates and zooplankton. Suitable tiny dry foods are accepted, but provide small live or frozen foods daily, such as newly hatched Artemia, Moina, or small worms. Actual particle size matters more than a general small-fish label.

Behaviour & compatibility

A species aquarium is preferable, although other very small, peaceful fishes can work. This is a loose social aggregation rather than a tightly coordinated school. Ten or more help distribute disputes and encourage confident behavior.

Males regularly spar during daylight, and damaged fins may occur within the group. Such behavior usually does not extend to other species, but a peaceful overall disposition does not eliminate male rivalry.

Sexual dimorphism

Males are slimmer and brighter, with red anal and caudal coloration absent in females. Brazilian males develop an extended anal fin, especially dominant individuals.

Breeding

Aquarium breeding has succeeded, and occasional fry may survive in a mature, densely planted tank. For greater survival, prepare a separate container with aged water and abundant fine spawning yarn, moss, or other finely divided plants. Lighting is unnecessary; a small air-driven sponge can provide gentle filtration if desired.

Condition adults before introducing a pair or one to two males with several females. More adults increase egg predation, and multiple males can distract each other instead of improving output. Remove the parents after two to three days; fry may become visible a day or two afterward.

Offer Paramecium or finely graded fry food around 5–50 μm initially. Introduce Artemia nauplii and microworms when the young can swallow them.

Notes

Specimens can arrive mixed with other wild-collected small fishes, so a shipment label does not establish the identity of every individual. At night the fish generally becomes pale rather than developing the strong bars or blotches seen in many other pencilfishes.