Taxonomy & naming
Chalceus macrolepidotus was described by the French anatomist Georges Cuvier in 1818, one of the earliest characins to be formally named. It is the type species of the genus Chalceus, a small group of large-scaled, silvery, surface-oriented characins historically placed in their own family, Chalceidae, distinct from the true tetras and from the piranha-and-pacu family Serrasalmidae. The genus name comes from the Greek chalkeos, "of bronze" or "coppery", a nod to the metallic sheen of the flanks; the species epithet macrolepidotus is Greek for "large-scaled", describing the conspicuously oversized scales that are the fish's most distinctive field mark.
Chalceus is a genus of only a handful of valid species, and identification within the genus rests on scale counts, fin colouration and body proportions rather than any single obvious trait, so museum-grade confirmation typically requires a specimen in hand. In the aquarium trade the species is most often sold simply as "pink-tailed characin" or "pink-tailed chalceus", a name that describes the rosy wash across the caudal fin of healthy adults.
Morphology
The pink-tailed chalceus has an elongated, laterally compressed, torpedo-shaped body built for sustained swimming near the surface rather than for cover-dependent stop-and-start movement. Its most obvious feature, and the source of its species name, is a covering of unusually large, coin-like scales that catch the light with a bright, coppery-silver sheen along the flanks. The upturned mouth and forward-set eyes are typical of a fish that feeds and watches from just under the surface film.
FishBase records a maximum standard length of 10 in, making this a substantially larger fish than most aquarium characins and well above the size of a typical tetra. Fins are proportionally large for a fast-swimming shoaler, and adults develop the pink-to-red wash on the caudal fin (and sometimes the anal fin) that gives the species its common name; juveniles are plainer silver. No reliable external difference between males and females has been documented for this species.
Habitat
Chalceus macrolepidotus is native to northern South America, recorded from the Rio Negro and Orinoco River basins and across the Guianas, including Guyana, Suriname and French Guiana, with records also reaching Colombia, Venezuela and Peru. It occupies the surface and near-surface layers of clear, fast-flowing, highly oxygenated rivers and streams — a habitat that shapes both its swimming style and its reputation as an exceptional jumper, since fish living at the air-water interface in flowing water are primed to clear obstacles and leap from danger.
Water across its range is warm tropical and well aerated, with FishBase and hobby sources placing it around 23-28 degrees C and, per Seriously Fish, a pH of roughly 6.0-7.5 and moderate hardness around 5-18 degrees H. This is not the soft, tannin-stained blackwater sometimes assumed for Guiana Shield fish; the species is specifically associated with clear, current-rich, oxygen-saturated water rather than static or heavily acidic pools.
Feeding
In the wild, Chalceus macrolepidotus is documented taking insects and aquatic crustaceans from the surface and near-surface layers it patrols, consistent with its upturned mouth and its habit of holding station just under the water's film. It is a carnivorous, actively hunting shoaler rather than a grazer or detritivore, and it forages readily in open water rather than picking at biofilm or vegetation.
In the aquarium it takes a range of meaty foods well — prawn, mussel, bloodworm and earthworm are all reported as accepted fare, alongside quality prepared foods offered at or near the surface. Because it is an active predator of a real size, small fish sharing the tank are at genuine risk of being eaten rather than merely harassed, and tankmates should be chosen with that in mind.
Mating
Documented detail on courtship behaviour in Chalceus macrolepidotus is sparse. Seriously Fish notes only that the species is an egg-scatterer, releasing eggs among vegetation, which implies the fish pairs off or otherwise associates around spawning sites without building a nest, but no detailed account of courtship display, colour change or pairing behaviour appears in the sources available for this species. No external sexual dimorphism has been reliably documented, and hobbyist accounts do not describe a reliable way to visually sex the species outside of spawning condition.
Breeding
Chalceus macrolepidotus is reported as an egg-scattering species: mature females can release very large numbers of eggs, cited at up to around 2,000, broadcast among fine vegetation rather than deposited in a guarded nest, and there is no parental care of eggs or fry. Achieving this in the aquarium in practice requires a very large, densely planted tank to accommodate the size and activity level of a conditioned group, which is one reason successful captive spawning is only occasionally reported by hobbyists despite the natural egg-scattering behaviour being straightforward in principle.
Where spawning has been reported, fry are raised on brine shrimp nauplii once free-swimming. Overall, the species should be treated as rarely bred in the home aquarium — most specimens in the trade are wild-collected or come from limited hobbyist efforts rather than commercial-scale captive breeding.
In the aquarium
This is not a small, easy-to-house characin: at up to 10 in, Chalceus macrolepidotus needs a genuinely large aquarium with plenty of open swimming space in the upper water column, and because it is documented as an exceptional jumper, a tight-fitting, gap-free cover is essential — a fish that lives at the surface of fast water in the wild will readily clear an open top. Strong water movement and high oxygenation, matching its native fast-flowing river habitat, are worth replicating rather than treating as optional.
Socially it is flexible but not forgiving of poor planning: it can be kept solitary or in a proper group of six or more, but smaller groups of two to five tend to result in persistent fighting, so a keeper should commit to one extreme or the other. It can cohabit with robust, similarly sized cichlids and catfish, but it is a genuine predator toward smaller fish and will eat anything it can fit in its mouth, and as it matures it becomes territorial toward other surface-dwelling fish. This combination of size, jumping ability and predatory temperament makes it a species for an experienced keeper with a large, secure setup rather than a casual community-tank addition.
Conservation
Chalceus macrolepidotus is assessed by the IUCN Red List as Least Concern, reflecting a wide distribution across the Rio Negro, Orinoco and Guiana Shield drainages and no evidence of significant population decline. The species supports commercial fisheries in parts of its range and is also held in public aquaria, both of which point to healthy, harvestable wild populations rather than a fish under acute pressure.
As with other Guiana Shield and upper Amazon-Orinoco fish, the longer-term watch items are the general pressures on those river systems — mining-related sedimentation, deforestation and water-quality change — rather than any threat specific to this species. No targeted conservation programme for Chalceus macrolepidotus is documented in the sources available here.