Taxonomy & naming
Characidium brevirostre was described by the French ichthyologist Jacques Pellegrin in 1909. It sits in the genus Characidium, within the subfamily Characidiinae of the family Crenuchidae — the South American darter characins — in the order Characiformes. Crenuchidae is a small, distinct family from the far larger and better-known Characidae (the true tetras); its members are unified by a benthic, darting lifestyle rather than by shoaling in open water.
The genus Characidium is species-rich, with roughly 60 to 65 recognised species distributed across Amazonian, Orinoco and coastal South American drainages, and it remains an area of active taxonomic work; regional revisions have split and redescribed several similar-looking stream populations over the past few decades. Characidium brevirostre is known specifically from coastal river systems in Amapá state, Brazil, and identification within the genus rests on fine details of scale counts, fin-ray formulas and the pattern of dark blotches along the flank — features that are difficult to assess without a specimen in hand, so field identification of Characidium to species level is genuinely uncertain in many cases.
Morphology
Characidium brevirostre is small even by the standards of its own genus: FishBase records a maximum length of 1.5 in standard length, placing it among the more diminutive Characidium species. Like other darter characins it has an elongate, cylindrical to slightly compressed body built for holding position in flowing water and for short, rapid dashes rather than sustained swimming — a body plan that converges, superficially, on unrelated darter-like fish from other continents.
The genus as a whole typically shows a series of dark blotches or a broken lateral stripe along the flank over a pale background, and Characidium species characteristically perch on their paired fins — resting propped on the substrate on the pelvic and anal fins rather than hovering in midwater, a habit that is one of the clearest field marks separating them from typical tetras. Precise colouration and marking detail for C. brevirostre specifically is not covered in the sources reviewed for this article; data sparse.
Habitat
Characidium brevirostre is native to coastal stream systems in Amapá, in far northern Brazil near the mouth of the Amazon, rather than to the main Amazon channel itself. FishBase records a temperature range of 72–79 °F and a pH range of 5.8–7.2 for the species, indicating soft-to-moderate, mildly acidic to neutral water typical of small forest and coastal streams in the region — cooler and less extreme than the classic blackwater conditions associated with some Amazonian tributaries.
Darter characins in general favour clear, well-oxygenated, flowing water over sand, gravel or rocky substrate, where their perching, fin-propped posture and rapid dart-and-rest movement suit a benthic, current-adapted lifestyle. FishBase assigns the species a trophic level of 3.2, consistent with a small invertebrate-feeding predator low on the local food web.
Feeding
Characidium brevirostre is a micro-predator, not a generalist grazer or scavenger. Its trophic level of 3.2 on FishBase and its family-wide reputation both point to a diet of tiny aquatic invertebrates — insect larvae, micro-crustaceans and similar benthic and drifting prey — taken in short, targeted strikes from its resting perch on the substrate rather than picked up by constant cruising.
In the aquarium this translates directly: keepers report the species is omnivorous in the sense that it will sample a range of foods, but it clearly prefers small live or frozen items such as bloodworm, brine shrimp and other micro-fauna, and it frequently ignores dry flake altogether. Anyone keeping this fish should plan on live or frozen micro-foods as the staple, not flake, and should expect a fish that forages actively along the bottom rather than at the surface.
Mating
No courtship or pairing behaviour has been documented for Characidium brevirostre specifically in the sources reviewed for this article. Practical Fishkeeping's overview of the genus describes Characidium broadly as substrate egg-scatterers that spawn over hard substrate with no pair-bonding beyond the act of spawning itself, but this is a genus-level generalisation rather than a confirmed account for this species — no breeding report, wild or captive, exists for C. brevirostre in the material available here. Data sparse.
Breeding
Breeding in Characidium brevirostre itself is undocumented — FishBase explicitly notes the breeding mode is not recorded for this species, and no aquarium spawning account for it was found. What is known comes from the genus as a whole: Characidium species are reported as egg-scatterers that release eggs over hard substrate with no parental care, with eggs hatching in roughly 30–40 hours and fry that need infusoria and then baby brine shrimp to get started.
This genus-level pattern should not be read as confirmed for C. brevirostre. Unlike the cave- and leaf-spawning crenuchids such as Crenuchus spilurus, which show brief male care of a small clutch, the stream-darting Characidium species are understood as parental-care-free scatterers — but until someone documents a captive spawning of this particular species, that remains an inference from relatives rather than an established fact for C. brevirostre.
In the aquarium
Characidium brevirostre is described as a hardy aquarium fish that adapts well to captivity, and its adult size of 1.5 in makes it a genuine nano species — a small, well-planted or rock-and-sand-scaped tank with gentle to moderate flow and good oxygenation suits it far better than a large community setup. It is reported as an inactive, retiring fish that spends much of its time hiding among rocks and plants rather than patrolling the tank, so cover and a calm environment matter more than swimming space.
Water should be kept soft to neutral and mildly acidic, tracking the wild range of roughly pH 5.8–7.2 and 72–79 °F — noticeably cooler than many tropical Amazon species, so this is not a fish to keep at typical discus- or angelfish-range temperatures. Feed small live or frozen foods rather than relying on flake, which this species often ignores. One general genus-level caution is worth carrying over here: some Characidium can be territorial or temperamental with similar bottom-dwelling tankmates in a mixed tank, so a species tank or a very calm community with plenty of sightline breaks is the safer choice.
Conservation
Characidium brevirostre is assessed as Least Concern by the IUCN Red List, with the assessment dated 8 April 2020. This reflects a species restricted to coastal stream systems in Amapá, Brazil, rather than the vast, well-studied Amazon mainstem — a genuinely restricted range, but one without a documented pattern of decline or major threat in the sources reviewed here.
As with many small-bodied, range-restricted stream characins, ongoing habitat pressures in Amazonian and coastal Brazilian drainages — deforestation, water-quality change and local development — are the kind of long-term watch items relevant to species like this even without a specific threat cited in its current assessment. There is no indication in the sources reviewed that C. brevirostre is targeted for the aquarium trade at meaningful volume; it appears to be a scarcely traded species known mainly from scientific and specialist hobbyist coverage.