Taxonomy & naming
Characidium boehlkei was described by the French-American ichthyologist Jacques Géry in 1972 and placed in the genus Characidium, one of the largest genera in the family Crenuchidae — the "South American darters," a family that also contains the very different-looking sailfin characins (Crenuchus, Poecilocharax). The Catalog of Fishes (Eschmeyer, California Academy of Sciences) treats Characidium as the authority for the genus placement; nothing in the available sources suggests a later reclassification for this species, so it remains simply Characidium boehlkei.
The species epithet honours the American ichthyologist James E. Böhlke, a prolific describer of Neotropical fishes at the Academy of Natural Sciences of Philadelphia. Characidium as a genus is taxonomically dense and historically confused — many species were long lumped under names such as C. fasciatum before finer distinctions were resolved — so field identification of C. boehlkei against its many congeners rests on close comparison with the original description rather than general appearance alone.
Morphology
Like other members of its genus, Characidium boehlkei is a small, slender, torpedo-shaped fish, with sources for the genus giving a maximum size under 4 in standard length. The body is built for perching and darting rather than sustained open-water swimming: the pectoral and pelvic fins are enlarged and used to prop the fish up off the substrate, a posture and habit that gives the group its common name of "darters."
Colouration in Characidium varies with habitat — genus accounts describe individuals from vegetated rivers running greener and those from rocky streams running darker — typically overlaid with a broken lateral band or series of blotches that provide camouflage against a mottled stream bed. Precise colour pattern and fin-ray counts specific to C. boehlkei are not detailed in the available sources; keepers should treat photographs of confirmed, correctly identified specimens as the best guide.
Habitat
Characidium as a genus is distributed across clear streams throughout South America, with sources describing a broad range running from the Río de la Plata drainage north to the Orinoco. Within that range the fish favours flowing, well-oxygenated water — clear to lightly tannin-stained, sometimes blackwater — over silty standing water, consistent with its perching, current-facing lifestyle.
Genus-level habitat data give a temperature range of roughly 64–81 °F, pH 5.5–7.5 and moderate hardness (GH roughly 5–25), which is a wider window than many Amazonian blackwater specialists and reflects the group's spread across both tropical and cooler subtropical drainages. No locality data specific to C. boehlkei is given in the available sources beyond its placement in this wide genus range, so keepers should not over-specify its exact home water without a confirmed collection record.
Feeding
Characidium species are micro-predators, not grazers or flake-eaters. In the wild the genus takes tiny aquatic insects, insect larvae, and small crustaceans picked from the stream bed and drifting current, and sources note explicitly that darter characins often will not readily take flake food.
In the aquarium this translates into a need for small live or frozen foods offered regularly: mosquito larvae, cyclops, daphnia, brine shrimp and bloodworm are all cited as suitable. Because the fish is a bottom-perching sit-and-wait feeder rather than a mid-water forager, food needs to reach the lower part of the tank, and frequent small feedings suit its natural feeding rhythm better than occasional large ones.
Mating
Detailed courtship behaviour specific to Characidium boehlkei is not documented in the available sources. What is recorded is a breeding trigger common to soft-water Neotropical stream fish: conditioning on live and frozen micro-foods followed by a shift to softer, more acidic water, which brings fish into spawning condition.
External sexual dimorphism for the species is not described in the sources consulted; keepers of the genus generally rely on body shape and conditioning behaviour, and possibly females appearing fuller when gravid, rather than any documented colour or fin difference between the sexes.
Breeding
Characidium is not a mouthbrooder or bubble-nest builder. Practical hobby accounts for darter characins as a genus describe an egg-scattering strategy over the substrate and fine-leaved plants, with a breeding setup of soft, acidic water, cover such as Java moss, and gentle-to-moderate water movement (for example from a sponge-filtered inlet) recommended to encourage spawning.
No account in the available sources confirms captive breeding reports specific to C. boehlkei itself, parental care, clutch size or fry-rearing details for this species — that level of detail is documented for the genus in general rather than this species in particular, and should not be assumed to apply exactly. Prospective breeders should treat the genus-level protocol as a starting point, not a guarantee, for this species.
In the aquarium
Characidium boehlkei suits a nano-to-small aquarium sized to its modest maximum length of under 4 in; genus-level care guidance calls for a minimum of around 23.5 in tank length. As bottom-oriented perchers, darter characins need a tank furnished with fine gravel or sand, smooth stones, and current from the filter outflow to give them the flowing-water feel of a stream. Cover is essential: the fish are described as expert jumpers, so a tight-fitting lid is not optional.
Because the species is a micro-predator that often ignores flake, keepers need to commit to a rotation of small live or frozen foods rather than expecting it to adapt to standard community fare. It is not documented as aggressive or fin-nipping and its small size and bottom-dwelling habit make it a reasonable companion for other peaceful nano or small stream-community fish, though specific tankmate compatibility for C. boehlkei itself is not detailed in the available sources. Given how easily this genus is confused with close relatives, buyers should seek out correctly identified stock where possible.
Conservation
No IUCN Red List assessment for Characidium boehlkei was found in the available sources, so its conservation status is recorded here as Not Evaluated. This is common among small, range-restricted or taxonomically dense South American stream genera that have not been through a formal Red List review, and it does not by itself indicate the species is at risk or is secure — simply that no assessment exists yet.
As with many obscure characins collected from clear headwater and tributary streams, the main long-term watch items for a species like this are generic to its habitat type: deforestation-driven siltation, water-quality change and stream-flow alteration in South American drainages, rather than any documented species-specific pressure.