Taxonomy & naming
The Bolivian cory was described in 1983 by Han Nijssen and Isaäc Isbrücker, the Dutch pair who between them named a large share of the corydoradine catfishes during the late twentieth century. The type material came from the Mamoré River system in Bolivia, and the species was placed in Corydoras Lacépède, 1803 — the sprawling genus of South American armoured catfishes in the family Callichthyidae (subfamily Corydoradinae) that, for most of the hobby's history, held essentially all the 'cory cats'.
That genus had become a taxonomic catch-all of well over 170 species, and molecular work showed it was not a single natural lineage. In 2024 Dias, Tencatt and colleagues published a phylogenomic revision (Zoological Journal of the Linnean Society) that split Corydoras into several genera — among them Brochis, Hoplisoma, Osteogaster and Gastrodermus. Under that scheme the Bolivian cory becomes Brochis geryi, and that is the combination now carried by Eschmeyer's Catalog of Fishes and by FishBase. The change is recent and not yet universal in aquarium usage, so we keep the familiar 'Corydoras geryi' as the heading while recording the current valid combination. The species name honours Dr Jacques Géry (1917–2007), the French physician and ichthyologist whose work on Neotropical fishes was prolific and influential.
Morphology
This is a small cory, reaching roughly 2.5 in in standard length — so a little under 3 in in total length once the tail is included. The body is the typical corydoradine shape: short, deep and arched along the back, flat-bellied, and encased not in scales but in two overlapping rows of bony plates (scutes) that meet in a ridge down each flank. The head is a blunt, hard helmet, and the small, downturned mouth is fringed with sensory barbels used to taste and probe the substrate.
The colour is understated: a pale, greyish to fawn ground broken by fine, scattered dark speckling that can coalesce into faint reticulation over the upper body, with a metallic sheen on the flanks under good light. As in other corys, the dorsal, pectoral and adipose fins each bear a stiff leading spine — a defensive structure that can deliver a sharp jab and snag in a net. Reliable external sex characters are subtle; as is usual in the group, mature females tend to be larger and broader-bodied than males, most obviously when viewed from above and when in spawning condition.
Habitat
Corydoras geryi is recorded from the Mamoré River basin, a major tributary system of the upper Madeira drainage in the Bolivian Amazon. These are warm, lowland tropical freshwaters, and the fish is a benthic, demersal species of the kind that favours the shallow margins of streams and rivers over soft sand and mud with leaf litter and submerged wood.
FishBase gives a broad working envelope for the species in line with other lowland corys: temperatures of about 72–79 °F, a pH band from acid to slightly alkaline (roughly 6.0–8.0) and soft to moderately hard water (around 2–25 dH). Like other members of the subfamily it is a facultative air-breather, able to dart to the surface and absorb atmospheric oxygen through a modified, vascularised hindgut — an adaptation that lets corys persist in the warm, oxygen-poor pools and shrinking dry-season channels that are common across the Amazon lowlands.
Feeding
Like its relatives, the Bolivian cory is a benthic omnivore and detritivore that works the bottom continuously, burying its snout and barbels in soft sand to taste out small invertebrates, insect larvae, worms, micro-crustaceans, fallen organic matter and the film of detritus, then expelling cleaned substrate through the gill openings. It is an opportunist rather than a specialist, and that broad diet is part of what makes corys generally hardy. In the aquarium it readily takes sinking pellets and granules, frozen and live foods such as bloodworm and brine shrimp, and anything edible that settles to the bottom — but it should be fed deliberately rather than left to scavenge leftovers.
Mating
No detailed account of spawning in Corydoras geryi specifically has been published, but corydoradine catfishes share a distinctive and well-studied courtship that almost certainly applies here. They are egg-laying shoalers with no pair bond. When a female is ready she cleans a site, the group becomes active, and a male takes up the classic 'T-position' at right angles to her head; the female appears to take milt into her mouth, and sperm is thought to pass rapidly through her gut to fertilise the few eggs she cradles in a basket formed by her clamped pelvic fins. She then presses those eggs onto the cleaned surface, and the sequence repeats a few eggs at a time.
Breeding
There is no documented aquarium breeding record specific to C. geryi, and the species is uncommon in the trade, so what follows is the general corydoradine pattern rather than a species-confirmed protocol. Spawning in this group is typically triggered by a large, cooler water change that mimics the onset of the rainy season. The adhesive eggs are laid in small batches and scattered across firm surfaces; the adults give no parental care and will eat the eggs, so breeders move either the eggs or the parents. Eggs generally hatch in three to five days depending on temperature, and the fry take microworm, baby brine shrimp and powdered foods once the yolk sac is absorbed. Because the species is so rarely kept, the fish offered for sale are most often wild-collected rather than captive-bred.
In the aquarium
The Bolivian cory makes the same demands as any small cory, and meeting them is straightforward. First, it is a shoaling fish that is genuinely stressed when kept singly or in pairs — keep a group of six or more and it will be far more confident and active. A group is comfortable in a tank of around 23.5 in / 20 US gal or more, where bottom area matters more than height.
Second, substrate is functional, not decorative: provide soft sand or very smooth, rounded fine gravel, because corys feed by sifting and sharp or coarse gravel abrades and infects the barbels, leaving the blunted, eroded faces that are a classic sign of poor husbandry. Keep the bottom clean. Water should be warm but not hot (about 72–79 °F), well-filtered and well-oxygenated, with gentle flow and regular changes; the species tolerates a wide pH and hardness range. It is utterly peaceful and suits a quiet community of tetras, small rasboras, dwarf cichlids and the like — never tankmates large enough to bully or eat it. Two standard cautions apply: the fin spines tangle in nets, so a cup is safer for moving them, and a badly stressed cory can release a skin toxin that, in the small volume of a bag or bucket, can kill the whole group during transport.
Conservation
Corydoras geryi is assessed by the IUCN as Least Concern (assessment dated 2020). It is a small, demersal freshwater fish of the Mamoré system, and the assessment reflects a lack of evidence of major decline rather than detailed population monitoring. As with all Amazon-lowland fishes, the broad regional pressures — deforestation, agricultural run-off, mining and the damming of the Madeira system — degrade the shallow marginal habitats it depends on, but at present the species is not considered threatened. Collection for the aquarium trade is minor, since it is only occasionally exported.