Taxonomy & naming
Phenacobrycon henni was described by the American ichthyologist Carl H. Eigenmann in 1914 as part of his expansive survey of South American characins. The species is the sole member of the genus Phenacobrycon, which is placed within the family Characidae. Eschmeyer's Catalog of Fishes records the valid name as Phenacobrycon henni (Eigenmann, 1914); the parenthetical authority reflects the original placement in a different genus from which the species was later moved to Phenacobrycon.
The genus name Phenacobrycon combines the Greek phenacos (deceiver) with brycon, a large and familiar Neotropical characin genus — a construction that signals resemblance to Brycon while hinting at superficial rather than close relationship. The epithet henni honours a collector or patron associated with Eigenmann's surveys, in keeping with the patronymic naming conventions common in early twentieth-century Neotropical ichthyology. Detailed information on type locality and type material resides in the original 1914 description and in Eigenmann's broader Indiana University monographs on South American fishes.
Morphology
Phenacobrycon henni is a small, elongate characin with the compressed body plan typical of many small tetras in the family Characidae. Like other characins it bears an adipose fin, the hallmark of the order Characiformes, positioned between the dorsal and caudal fins. Specific meristic data — scale counts, fin-ray formulae, and body proportions — are found in the original description by Eigenmann, who provided detailed measurements of the type material.
Published size records are sparse in secondary sources. The species is small by characid standards, consistent with the dimensions typical of tetras encountered in the lowland streams of South America. Coloration in preserved specimens — the basis for most historical accounts — is less informative than live fish would be; the species is rarely photographed alive, and its live coloration is not well characterised in the accessible literature.
Habitat
Phenacobrycon henni originates from South America. Eigenmann's 1914 material was collected from drainage systems in what is now Colombia, consistent with the broad collecting range of his surveys across the Magdalena and associated lowland river systems. The species likely inhabits slow-moving to moderate streams and river margins, the habitat typical of small Neotropical characins, but detailed in-situ habitat notes are sparse.
Small lowland tetras in this part of South America typically occur in warm, soft, slightly acidic to near-neutral waters in shallow, often well-vegetated or shaded stream sections. Without specific water chemistry records for Phenacobrycon henni, these generalisations from the regional fauna are the best available guide. Published distribution data are limited, and the species' precise range within South America is not comprehensively mapped in accessible databases.
Feeding
No specific dietary studies of Phenacobrycon henni have been published in the accessible literature. By analogy with closely sized and ecologically positioned tetras in the Characidae, the species is presumed to be an opportunistic omnivore in the wild, taking small invertebrates, insect larvae, and organic matter in the water column and at the surface.
In captivity, small characins of this type typically accept standard tetra fare: fine-grade flake and micro-pellets, small frozen or live foods such as Daphnia, baby brine shrimp, and microworms. Given the species' rarity in the trade, husbandry accounts are nearly absent; any keeping would best be approached along conservative small-tetra lines with a varied, protein-supplemented diet.
Mating
No published observations of courtship behaviour in Phenacobrycon henni are available. Small tetras in the Characidae are overwhelmingly egg-scatterers, and there is no reason to expect a different strategy in this genus. In typical egg-scattering characins, males pursue ripe females and spawning occurs in open water or among fine-leaved vegetation, with eggs falling or adhering among plants and receiving no further parental attention.
In the absence of species-specific records, the reproductive biology of Phenacobrycon henni should be treated as inferred rather than documented. Breeders or researchers working with the species would be in a position to establish whether any distinctive courtship features are present.
Breeding
Phenacobrycon henni has not been documented as a regularly bred species in the aquarium hobby, and no detailed breeding accounts appear in the accessible literature. The egg-scattering mode inferred for the genus would suggest that, if spawning were achieved, the general approach used for similarly small tetras would apply: a separate shallow breeding tank, soft and slightly acidic warm water, fine-leaved plants or synthetic spawning mops, and removal of adults after spawning to prevent egg predation.
Adhesive or semi-adhesive eggs among fine-leaved plants and no parental care are the expected pattern. Incubation times and fry sizes, if broadly comparable to other small Characidae, would be on the order of two to four days to hatching, with very small fry requiring infusoria-grade first foods. These remain inferences until documented observations become available.
In the aquarium
Phenacobrycon henni is essentially unknown in the mainstream aquarium hobby. It does not appear in regular commercial supply, and husbandry information based on direct experience with the species is not available in the accessible literature. Any aquarist obtaining specimens would be working largely from inference and from experience with broadly comparable small tetras.
On general small-tetra principles, a group of six or more would be appropriate to express natural shoaling behaviour, in a well-planted aquarium with subdued lighting, gentle filtration, and soft, warm, slightly acidic water. Peaceful, similarly sized tankmates would be required, and careful attention to acclimatisation and water quality would be especially important given the species' obscurity and the likelihood that specimens would come from wild or rarely bred stock. Any reliable first-hand observations would be a genuine contribution to the literature on this little-known fish.
Conservation
Phenacobrycon henni has not been assessed by the IUCN Red List, and no conservation status is currently assigned to the species. It is not known to appear on CITES appendices or in major national red-list databases. The absence of an assessment reflects limited data rather than confirmed security.
As a species with a restricted described range, apparently rare in collections, and with minimal coverage in modern monitoring programmes, Phenacobrycon henni falls into the category of data-sparse Neotropical fishes for which conservation concern cannot be ruled out. Any modern collection records, habitat notes, or population observations would be valuable to establishing whether a formal IUCN assessment is warranted.