Taxonomy & naming
Corydoras robustus was described by Han Nijssen and Isaäc Isbrücker in 1980, in the Netherlands Journal of Zoology, as part of their wider review of the genus. The type locality, given in Eschmeyer's Catalog of Fishes, is a creek flowing into the Rio Ipixuna, in the Rio Purus system, about 19 mi west of Humaitá, in Amazonas State, Brazil — squarely in the interfluve between the lower Purus and the Madeira. The name is the Latin robustus, 'robust' or 'strong', for the species' heavy, sturdy build.
For four decades it sat in Corydoras Lacépède, 1803, the enormous genus that came to hold the great majority of the hobby's 'cory cats'. Molecular work showed that genus to be unnatural, and in 2024 Dias, Tencatt and colleagues split it into several genera. Under that revision the robust cory moves to the resurrected genus Brochis — the clade of broad-headed, large, many-plated corys such as the emerald and giant brochis — giving the current valid combination Brochis robusta. The Catalog of Fishes records it as valid under that name, and FishBase has adopted it. The aquarium trade still says 'Corydoras robustus', so we keep that heading while noting the new combination.
Morphology
This is a large cory by the standards of the old genus, reaching about 3 in in standard length and noticeably stout — deep-bodied, thick through the shoulders and powerfully built, which is the quality the name captures. It has the moderately elongate, somewhat pointed snout characteristic of the 'long-snouted' corys, rather than the blunt face of the common bronze and peppered kinds. Like all members of the family it is armoured rather than scaled, with two longitudinal rows of overlapping bony plates down each flank, a hard bony head, and three pairs of barbels framing the downturned mouth.
Its placement in Brochis reflects body form: that lineage contains the broad, large, many-plated corys, and robustus shares their general heavy build. The dorsal, pectoral and adipose fins each bear a stiff spine, as in all corys. Colouration in this species is comparatively plain — a brownish to grey body with darker mottling and fin markings rather than the bold spots or stripes of the showier corys; it is a fish that earns its place by size and form more than pattern.
Habitat
Corydoras robustus is native to the southwestern Brazilian Amazon, in the Rio Purus and Rio Madeira drainages of Amazonas State. Its type locality is a small creek tributary to the Rio Ipixuna within the Purus system, near Humaitá. These are lowland Amazonian waters: the species inhabits streams and the quieter margins of rivers over soft sand and mud with leaf litter and submerged wood, the typical habitat of bottom-dwelling corys.
The water is warm, soft and acidic to near-neutral. FishBase gives a temperature range of roughly 72–79 °F, a pH from about 6.0 to 8.0 and soft to moderately hard water (around 2–25 dH), figures consistent with the broad envelope corys tolerate across the central Amazon. As with most corys it is a fish of shallow, slow-flowing or still water rather than fast main channels, foraging over the bottom in the warm, often tannin-stained shallows.
Feeding
No detailed dietary study has been published for Corydoras robustus, but it is a benthic omnivore and detritivore like the rest of its family. It forages over sand and leaf litter, using its barbels and snout to taste and sift the substrate for small invertebrates, insect larvae, worms, micro-crustaceans, fallen seeds and the organic detritus packed between sand grains and among fallen leaves. The somewhat elongate snout suits probing a little deeper into soft substrate than the blunt-faced corys manage. As an opportunist it takes whatever small animal and plant matter the streambed provides; in captivity its larger size means a correspondingly larger appetite for sinking foods.
Mating
The spawning behaviour of Corydoras robustus has not been specifically documented, but corys are strikingly uniform in this respect and it can be expected to follow the genus pattern. They are egg-laying shoalers without pair bonds. A receptive female cleans a spawning surface and the group grows active; a male adopts the classic 'T-position', aligning his body at right angles to the female's head, and she appears to take his milt while holding a small clutch of eggs in a basket formed by her clasped pelvic fins. She then carries those eggs to the cleaned surface and presses them down before the sequence repeats. As a larger species, robustus would be expected to lay correspondingly larger eggs than the smaller corys, but no spawning account confirms the details for this fish.
Breeding
Corydoras robustus is not a commonly bred aquarium fish, and there is no well-documented captive-breeding account to draw on; what follows is the expected genus pattern rather than confirmed behaviour for the species. Corys generally lay adhesive eggs in small batches, scattered across firm surfaces such as wood, stones, plants or the aquarium glass, with spawning often triggered by a cool, large water change that imitates the onset of the rainy season. They provide no parental care and will eat their own eggs, so a breeder must separate eggs from adults. Eggs of comparable species hatch within a few days, after which the fry take microfoods and small live foods such as baby brine shrimp. Because this is a larger, less frequently kept cory, reliable breeding information is correspondingly scarce.
In the aquarium
Corydoras robustus is an uncommon import and very much a specialist's fish rather than a standard shop cory, but its needs are those of the genus scaled up for a larger animal. It is a shoaling fish and should be kept in a group of six or more; like all corys it is stressed kept singly or in pairs. Because it is a big, active cory it needs a correspondingly larger tank with plenty of open bottom area — footprint matters far more than height. Provide soft sand or very smooth fine gravel, never sharp or coarse substrate, which abrades the barbels corys depend on for feeding and leads to infection and the blunted faces that signal poor husbandry.
Keep the water warm (around 72–79 °F), clean, well-filtered and well-oxygenated, with the gentle current and regular water changes any catfish appreciates; it tolerates a broad pH and hardness range but does best in soft, slightly acidic to neutral water like its Amazonian home. It is peaceful and suits a community of similarly calm fish, though its size means it is better with medium tankmates than tiny nano species. The usual cory cautions apply: the stiff fin spines can catch in a net, so a cup is safer for moving them, and a badly stressed cory can release a skin toxin that, in the confined volume of a bag or bucket, can be lethal to the whole group, so transport them with care.
Conservation
Corydoras robustus is assessed by the IUCN as Least Concern, in an assessment dated 2018. It occupies the Purus and Madeira drainages of the central-southern Amazon, a large area, and although it is not a heavily traded species there is no evidence of any specific threat to its populations. As with all Amazonian freshwater fishes, the broad pressures on the basin — deforestation, agricultural and pastoral expansion, mining, pollution and the proliferation of dams on the Madeira and its tributaries — degrade the marginal stream habitats such bottom-dwellers rely on, and the lower Madeira in particular has seen major hydropower development. None of this currently places the species at risk, but its long-term security is tied to the health of the southwestern Amazon's tributary streams.