Taxonomy & naming
Corydoras potaroensis was described by the American ichthyologist George S. Myers in 1927, from material taken in the Potaro River — a tributary of the Essequibo in central Guyana — which remains the type locality and the source of the species' name. It was placed in Corydoras Lacépède, 1803, the vast genus of South American armoured catfishes in the family Callichthyidae, and stayed there for the better part of a century as one of the few cory species endemic to the Guiana Shield rather than the Amazon basin.
The genus Corydoras had grown to well over 170 species and molecular work showed it was not a single natural lineage. In 2024 Dias, Tencatt and colleagues published a large phylogenetic revision of the Corydoradinae that split Corydoras into several genera — among them Brochis, Hoplisoma, Osteogaster and Gastrodermus — and under that scheme the Potaro cory becomes Hoplisoma potaroense. Both FishBase and the Catalog of Fishes now carry the species under Hoplisoma. The combination is recent and the aquarium trade still says 'Corydoras potaroensis,' so we keep that as the heading while noting the current lineage placement. The species is also linked in the hobby to a similar undescribed form catalogued as C139 (Corydoras cf. potaroensis).
Morphology
This is a small cory, reaching only about 1.5 in in standard length — a dwarf even by the modest standards of the genus. The body is the familiar Corydoras shape: deep and short, flat-bellied, with a blunt, helmeted head and a downturned mouth ringed by three pairs of sensory barbels for tasting the substrate. In place of scales it wears two longitudinal rows of overlapping bony plates (scutes) down each flank, meeting along a ridge on the back.
The ground colour is a pale tan to greyish body marked with darker blotching and a pattern of spots and a broken lateral band, the precise expression of which varies between populations and with mood. As in all Corydoras, stiff leading spines stiffen the dorsal and pectoral fins; these are mildly venomous and can deliver a sharp jab to a careless hand or snag in a net. Males are slimmer than the rounder, broader-bodied females, a difference most obvious when the fish are in condition.
Habitat
Corydoras potaroensis is endemic to the Potaro River basin of central Guyana, part of the Essequibo drainage on the Guiana Shield. This is a region of clear to lightly tannin-stained rainforest streams running over sand and fine gravel, fringed with leaf litter and submerged wood, and the species is a shallow-margin fish of these quieter reaches.
The water it lives in is warm, soft and slightly acidic to near-neutral — broadly in the range of about 72–79 °F with a pH around 6.0–8.0 in the wider basin — though the forest streams it favours tend toward the softer, more acidic end. Like other Callichthyidae it is a facultative air-breather, able to dart to the surface and absorb atmospheric oxygen through a vascularised hindgut, which lets it cope in the warm, low-oxygen pools that form as shield streams shrink in the dry season.
Feeding
The Potaro cory is a benthic omnivore and detritivore in the usual cory mould. It forages continuously over sand and fine substrate, burying its snout and barbels to taste out small invertebrates, insect larvae, micro-crustaceans, worms and the organic film of detritus, then expelling cleaned sand through the gill openings. It is an opportunist rather than a specialist feeder, taking whatever the leaf-litter and sand of its streams provide. In the aquarium it accepts sinking pellets and tablets, frozen bloodworm and brine shrimp and other small foods, but — as with all corys — should be fed a varied diet of its own and never left to scavenge leftovers.
Mating
No detailed account of courtship in Corydoras potaroensis has been published, but there is no reason to think it departs from the well-studied pattern of the genus. Corydoras are egg-laying shoalers with no pair bond. When a female is ready she cleans a spawning surface and the group becomes active; a male takes up the classic 'T-position', aligning at right angles to the female's head, and she appears to take milt directly, the sperm passing rapidly through her gut to fertilise the few eggs she cradles in a basket formed by her pelvic fins. She presses each small batch onto the cleaned surface, and the sequence repeats until the clutch is laid.
Breeding
Corydoras potaroensis is not a commonly bred aquarium fish, and no widely documented captive-breeding protocol exists for it specifically; what is known is inferred from its close relatives. Spawning in the genus is generally triggered by a cool, large water change that mimics the onset of the rainy season. The adhesive eggs are laid in small batches on plants, wood, stones or the glass and receive no parental care — indeed the adults will eat them, so a breeder removes either the eggs or the parents. Eggs typically 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. As a small, range-restricted species it is far less often spawned than the commercial corys.
In the aquarium
Corydoras potaroensis is an uncommon import, more a collector's and biotope-keeper's fish than a staple, but its care follows the standard cory template with a bias toward soft, slightly acidic blackwater conditions reflecting its Guiana Shield home. It is a shoaling species that is stressed when kept alone or in pairs; keep six or more and they reward you with constant, confident foraging.
Given its small size — only about 1.5 in — a modest tank suits a group, but bottom area matters more than height. Soft sand is the right substrate: corys feed by sifting, and sharp or coarse gravel erodes and infects their barbels, leaving the blunted, stubby faces that signal poor husbandry. Add leaf litter, wood and gentle, well-oxygenated flow, keep the bottom clean, and aim for warm but not hot water (about 72–79 °F). It is utterly peaceful and well suited to a Guiana-themed community of small tetras and other calm fish. As with all corys, the fin spines can catch in nets (a cup is safer), and a badly stressed fish can release a skin toxin that, in the confined volume of a bag, may kill the whole group — so transport them with care.
Conservation
The IUCN Red List assesses Corydoras potaroensis as Least Concern (assessment dated 2020). Despite its small geographic range on the Potaro and wider Essequibo system, the drainage remains largely forested and relatively undisturbed compared with many Amazonian rivers, and the species is not heavily exploited for the aquarium trade. The pressures that loom over Guiana Shield freshwaters more broadly — gold mining and the mercury and sedimentation that come with it, deforestation and run-off — are nonetheless real, and because the fish is a narrow-range endemic, localized habitat damage in the Potaro basin would weigh more heavily on it than on a widespread cory. For now it is judged to be at low risk.