Taxonomy & naming
The bandit cory was described by Carl H. Eigenmann in 1914 as Corydoras metae, from material collected at Barrigona on the Río Meta in Colombia (the type locality is associated with Puerto Barrigón on the Río Humea). It has sat in Corydoras Lacépède, 1803 — the vast genus of South American armoured catfishes in the family Callichthyidae — for more than a century, and that is the name under which it is traded and bred worldwide.
The genus had grown unwieldy, with well over 170 species, and molecular work showed it was not a single natural group. In June 2024 Dias, Tencatt and colleagues published a large phylogenomic revision (Zoological Journal of the Linnean Society, DOI 10.1093/zoolinnean/zlae053) that split Corydoras into several genera — among them the resurrected Brochis, Gastrodermus, Osteogaster and Hoplisoma. Under that scheme the bandit cory becomes Hoplisoma metae (Eigenmann, 1914), placed in lineage 9; the Catalog of Fishes and FishBase now carry it under Hoplisoma, and Corydoras World lists the same combination. The change is recent and not yet universal, and the aquarium world still overwhelmingly says 'Corydoras metae,' so we keep that heading while noting the current combination. The name is also a long-running source of confusion in the trade: 'bandit cory' is applied loosely to several similarly masked species, most often the superficially identical C. melini (the 'false bandit'), so the label on a tank is no guarantee of which fish is inside.
Morphology
This is a small, deep-bodied cory reaching only about 2 in standard length — modest even by the genus's standards. Like all corys it is armoured rather than scaled: two rows of overlapping bony plates (scutes) run down each flank and the head is a hard, blunt helmet, with three pairs of short sensory barbels fringing the downturned mouth. Females grow larger and become noticeably rounder and broader-bodied than males, especially when gravid.
The ground colour is a pale pinkish-cream to fawn, and on it the markings do the work that gives the fish its name. A thick black bar runs vertically across the head through both eyes — the 'mask' or 'bandit' stripe. A second dark band starts at the nape, runs back along the top of the body, darkens over and around the dorsal fin, then continues along the upper flank to the caudal peduncle, where it turns sharply downward at the tail base. The dorsal fin carries a black edge and dark markings near its base. This pattern is the key to separating the true bandit from its mimic C. melini: in metae the back-stripe runs along the upper edge of the body and makes a sharp turn down only at the caudal peduncle without spilling onto the tail, whereas in melini the stripe runs straight and diagonally from the dorsal fin down onto the lower caudal fin. As in all corys, the dorsal, pectoral and adipose fins each carry a stiff, mildly venomous spine.
Habitat
Corydoras metae is endemic to the upper Río Meta basin in eastern Colombia — the Meta being a major tributary of the Orinoco — where it is recorded from clearwater and blackwater tributaries including the ríos Humea, Ocoa, Guatiquía, Manacacias and Metica. It appears to be absent from the lower Meta and has not been reliably confirmed from the Venezuelan side, making it a fairly narrowly distributed fish despite its familiarity in the hobby.
These are warm tropical streams of the Llanos and Andean foothills, typically flowing over soft sand with leaf litter, roots and submerged wood at the margins. Reported water is soft to moderately hard and acidic to neutral — roughly pH 6.0–7.5, hardness on the order of 90–215 ppm, and temperatures around 68–79 °F. Like all corys it is a facultative air-breather, darting to the surface to gulp air and absorb oxygen through a modified, vascularised hindgut, which lets it cope in warm, oxygen-poor shallows.
Feeding
The bandit cory is a benthic foraging omnivore. In its home streams it works the sandy bottom continuously, burying its snout and barbels to taste out worms, small benthic crustaceans, insect larvae and other invertebrates, along with fallen plant matter and the organic film of detritus, expelling cleaned sand through the gills as it goes. It is an opportunist rather than a specialist. In the aquarium it readily takes good-quality sinking dried foods together with small live and frozen items such as bloodworm and Tubifex; like all corys it should be fed a proper varied diet and never left to scavenge leftovers, a myth that leaves many 'cleanup' corys slowly starving.
Mating
Corydoras are egg-laying shoalers with no pair bond and a distinctive, well-studied courtship, and metae follows the family pattern. When a female is ready the group becomes active and she cleans a site — a leaf, a stone, the aquarium glass. A male positions himself at right angles to her head in the classic 'T-position,' and she appears to take his milt into her mouth; sperm is thought to pass rapidly through her gut to fertilise the few eggs she clasps in a basket formed by her pelvic fins. She carries each small batch to the cleaned surface and presses the sticky eggs into place, and the sequence repeats until the clutch is complete.
Breeding
The bandit cory is bred in the hobby, though it is a touch less prolific and a little more demanding than the ubiquitous bronze cory. A productive group skews toward more males than females — roughly two males per female is the usual recommendation — and spawning is typically triggered by a large (50–70%) water change with cooler water, mimicking the cool rain of the wet season, repeated daily until the fish respond. The adhesive eggs are deposited on the glass, plants and décor and receive no parental care; the adults will eat them, so breeders remove either the eggs or the parents. Eggs hatch in about three to four days, and the fry — after absorbing the yolk sac — take microworm, baby brine shrimp and powdered foods. They are reasonably hardy and grow steadily. Most fish in the trade today are commercially captive-bred.
In the aquarium
The bandit cory is a rewarding community fish, but it has the same real requirements as the rest of its genus. First, it is a shoaling species and is genuinely stressed when kept alone or in twos — keep six or more, and they reward you with constant, confident foraging. A group is comfortable in a tank of around 23.5 in with a generous floor area; footprint matters more than height.
Second, substrate is not decoration. Provide soft sand or very smooth, rounded fine gravel kept scrupulously clean: corys feed by sifting, and sharp or dirty substrate erodes and infects their barbels, leaving the stubby, blunted faces that are a tell-tale sign of poor husbandry. Add cover — wood, leaf litter, planting or caves — so the fish feel secure. Water should be warm but not hot (about 72–79 °F), well-filtered and well-oxygenated, soft to moderately hard and on the acidic-to-neutral side. They are utterly peaceful and suit tetras, rasboras, dwarf cichlids and other calm community fish, never anything large enough to bully them. Two cautions worth knowing: the fin spines can catch in nets, so a cup is safer; and a badly stressed cory can release a skin toxin that, in the confined volume of a bag or bucket, can kill the whole group, so transport them with care.
Conservation
Corydoras metae is assessed by the IUCN as Vulnerable (VU), under criteria B1ab(iii,v)+2ab(iii,v) in an assessment dated 5 October 2020. Unlike the sprawling, adaptable bronze cory, the bandit is a comparatively narrow-range endemic of the upper Río Meta system, and that restricted distribution is what places it at risk: the shallow tributary habitats it depends on are exposed to deforestation, agriculture, sedimentation, pollution and other pressures across the Colombian Llanos and Andean piedmont. Collection for the aquarium trade is a lesser concern now that the species is commercially bred, but its limited geographic footprint means habitat degradation, rather than abundance, is the deciding factor in its status.