Taxonomy & naming
Schwartz's cory was described by Fritz Rössel in 1963, in a paper on new and rare Corydoras from Brazil published in Senckenbergiana Biologica. The holotype was collected at the mouth of the Rio Purus in Amazonas, Brazil, which remains the type locality. The epithet honours Hans-Willi Schwartz (1909–1981), an ornamental-fish exporter based in Manaus who helped secure the original material — one of many aquarium-trade collectors whose names are scattered through the cory genus.
For sixty years it has been catalogued as Corydoras schwartzi, and the trade still uses that name almost universally. But the genus Corydoras had become an unwieldy assemblage of more than 170 species that molecular data showed was not a single natural lineage. The 2024 phylogenomic revision by Dias, Tencatt and colleagues (Zoological Journal of the Linnean Society) split the old genus and resurrected several names; under that classification this species becomes Hoplisoma schwartzi — Hoplisoma being neuter, though here the epithet is a personal name and so is unchanged. Eschmeyer's Catalog of Fishes now lists Hoplisoma schwartzi (Rössel 1963) as the valid combination. Because the change is recent and the hobby still says 'Corydoras schwartzi,' we keep that as the heading while noting the current name. A practical footnote: a closely similar, more heavily marked trade form circulates under the code CW028 ('super Schwartzi'), a reminder of how many near-identical, sometimes undescribed corys move through the aquarium market.
Morphology
This is a small, compact cory, reaching only about 1.5 in standard length (FishBase) — roughly 2–2.5 in total length — with females growing larger and markedly rounder than males, a difference best judged from above. It has the standard armoured-catfish build: two rows of overlapping bony scutes down each flank instead of scales, a hard blunt head, and three pairs of barbels around the downturned mouth.
The markings are what set it apart. The base colour is pale cream to light tan, crossed by a single bold, cleanly defined dark stripe that runs along the midline from behind the gill cover to the tail base. Above that stripe the upper body and head carry fine, discrete dark spots, and a dark mask passes through the eye. The dorsal fin is tall, carries a stout, pale leading spine, and is boldly marked with a dark blotch toward its front and upper part; the caudal fin is finely barred. It is most often confused with the three-line cory (Corydoras trilineatus), but schwartzi's stripe is bolder and cleaner and the head bears separate spots rather than the connected, maze-like reticulation of trilineatus. As in all corys the dorsal and pectoral fins bear stiffened, mildly venomous spines, and the species — like its relatives — is harmless to people beyond the sharp 'sting' of a careless handling.
Habitat
Corydoras schwartzi is native to the Rio Purus basin, a major southern tributary of the Amazon draining a vast area of western Brazil before joining the main river. That gives it a fairly localised distribution within the middle Amazon, centred on the Purus drainage rather than spread across the continent.
Its waters are the warm, shallow, slow-moving streams and tributaries of the basin, with soft sandy bottoms, submerged wood, and leaf litter that stains the water with tannins. These habitats are typically soft and slightly acidic and heavily shaded by riparian forest, with the fish foraging in groups across the sand. FishBase gives a captive envelope of roughly 72–79 °F, pH 6.0–8.0 and soft to moderately hard water; in practice it does best kept on the cooler, softer, slightly acidic side and is not a fish for hot discus-temperature tanks. Like all corys it is a facultative air-breather, periodically darting to the surface to gulp air and take up oxygen through a modified, vascularised hindgut — an adaptation to the warm, low-oxygen backwaters it lives in, and entirely normal behaviour to see in the aquarium.
Feeding
Schwartz's cory is a benthic omnivore and an active bottom forager. In the wild it sifts sand and leaf litter for small invertebrates, insect larvae, micro-crustaceans and organic detritus, taking a mouthful of substrate and expelling it through the gills as it works. It is an opportunist rather than a specialist. In the aquarium it readily accepts sinking pellets, tablets and larger flake that reaches the bottom, along with frozen and live bloodworm, Daphnia, Tubifex, grindal and white worm, the richer foods being valuable for conditioning a group toward spawning. It should be given its own dedicated food rather than relied upon to scavenge other fishes' leftovers or 'clean' the tank; a varied diet keeps it healthy and well-coloured.
Mating
Like the rest of the genus, schwartzi is an egg-laying shoaler with no pair bond and the characteristic cory courtship. When a female is ready the group becomes active and a male takes up the classic 'T-position,' lying at right angles to her head. According to accounts of the genus the female briefly holds the male's milt and a few eggs — typically two to four — in a basket formed by her pelvic fins, fertilising them in the process, then carries the small, very sticky batch to a cleaned surface and presses them into place. The pair repeats the cycle many times over, working around the spawning surfaces until a total clutch on the order of a hundred eggs has been laid.
Breeding
Schwartz's cory is regarded as moderately challenging to spawn — not as effortless as the bronze or peppered corys, but achievable with conditioning and the right cues. Breeders condition a group skewed toward more males than females on rich live and frozen foods, then trigger spawning with a large, cooler water change in soft, slightly acidic water, mimicking the rainy-season flush of the Amazon. Smooth broad leaves, flat rocks and the aquarium glass serve as egg-deposition sites. The adhesive eggs receive no parental care and the adults will eat them, so the eggs or the parents are separated after spawning; a few drops of methylene blue or an Indian almond leaf in the rearing water helps fend off the fungus that is the main threat to a clutch. Eggs hatch in roughly three to five days, and the fry — after their yolk sacs are absorbed — take microworm, baby brine shrimp and powdered foods, growing on with clean water and frequent small changes.
In the aquarium
Schwartz's cory is a hardy, peaceful community fish, a touch less bombproof than the commonest beginner corys but well within reach of anyone with a little experience. It is a shoaling species and must be kept in a group — at least six — or it hides and sulks; in numbers it shoals, forages confidently and spends far more time in the open. A group of six is comfortable in a tank of around 20 US gal or more, with bottom area mattering more than height.
Sand substrate is effectively mandatory: these fish probe and sift the bottom constantly, and rough or sharp grit erodes and infects their barbels over months, blunting the very tools they feed with. Fine sand also lets them show their full, entertaining sifting behaviour. Pair the open sand with driftwood, leaf litter and some shade from plants or floating cover, which suits a fish that comes from tannin-stained, shaded streams; a dark substrate also makes its bold stripe stand out. Keep the water warm but not hot (best around 72–79 °F), soft to moderately hard, clean and gently filtered, with stable parameters favoured over chasing perfect numbers. It is an ideal companion for small tetras, rasboras, pencilfishes, peaceful gouramis, otocinclus, shrimp and Apistogramma, and should be kept away from anything large or aggressive enough to bully or eat it. The familiar cory cautions apply: net spines can snag (a cup is safer), and a severely stressed fish can release a skin toxin that may prove lethal in the small volume of a bag, so move them with care.
Conservation
Corydoras schwartzi is assessed by the IUCN as Least Concern (assessment dated 2018, by Brazil's Chico Mendes Institute, ICMBio). Although its range is fairly localised to the Rio Purus drainage, the species is not considered to face significant threats at present, and much of the fish entering the trade is supplied through the ornamental fishery and increasingly through captive breeding. That status is not a guarantee of permanent security: the shallow, forested blackwater streams it depends on are exposed to the broad pressures on Amazonian freshwaters — deforestation, run-off, changing land use and infrastructure — and a basin-restricted fish is inherently more sensitive to local habitat loss than a continent-wide generalist. For now, though, Schwartz's cory is in no danger, and keeping and breeding tank-raised stock is the sustainable way to enjoy it.