Taxonomy & naming
Corydoras approuaguensis was described in 1983 by Han Nijssen and Isaäc Isbrücker, the two Dutch ichthyologists who between them named a large fraction of the world's corys. The type series came from the Approuague River in French Guiana, and the epithet is geographic, formed from the river's name with the Latin suffix -ensis ('belonging to'). It is a member of the family Callichthyidae, subfamily Corydoradinae — the South American mailed catfishes armoured in two rows of bony scutes.
The name stood as Corydoras approuaguensis for four decades. Because the genus Corydoras had grown to more than 170 species and proved not to be a natural group, Dias, Tencatt and colleagues revised the subfamily in 2024 (DOI 10.1093/zoolinnean/zlae053), splitting it into several genera and resurrecting Brochis for one of the long-snouted, deeper-bodied lineages. Under that classification approuaguensis was transferred to Brochis, and the Catalog of Fishes now gives the valid combination as Brochis approuaguensis (Nijssen & Isbrücker 1983). We display the fish under Brochis to reflect the current science, while keeping the long-familiar 'Corydoras approuaguensis' as the heading the trade and older literature still use.
Morphology
This is a long-snouted cory: the head draws out into an elongate, pointed muzzle rather than the blunt face of the common short-nosed species. It is a modest-sized fish, reaching about 2.2 in in standard length, with females typically growing a little larger and fuller-bodied than males. The body wears the standard Corydoradinae armour — two interlocking rows of lateral bony plates meeting along the dorsal ridge, a hard bony head, three pairs of barbels around the downturned mouth, and stiff, mildly venomous leading spines in the dorsal, pectoral and adipose fins.
In colour it is a pale, sandy fish overlaid with fine dark speckling, well camouflaged against the bright sand it lives on. The feature that gives it both its English name and a handy field mark is the caudal fin, which is crossed by a series of dark bars — the 'zebra' tail — a pattern that helps distinguish it from the similar long- and short-snouted corys it co-occurs with in the same rivers.
Habitat
Corydoras approuaguensis is endemic to the Approuague River basin in French Guiana, one of the clear, tea-stained rivers draining the Guiana Shield to the Atlantic. It is a fish of moving water and clean substrate: it is reported as abundant in the backwaters of sandy beaches just downstream of rapids, and is also found in creeks with sandy-to-rocky bottoms strewn with some plant debris, typically over sand traversed by a strong current.
These are warm, clear, soft-water habitats. Reference parameters for the species give a temperature range of roughly 72–79 °F, a pH from acidic to slightly alkaline (about 6.0–8.0) and soft to moderately hard water. Like the rest of the subfamily it is a facultative air-breather, surfacing to gulp atmospheric air and absorbing oxygen across a vascularised hindgut. In its native rivers it is recorded sharing the sandy bottoms with the short-snouted Corydoras melanistius brevirostris and with Corydoras spilurus.
Feeding
Corydoras approuaguensis is a benthic omnivore and detritivore, like its relatives. Its long snout is a feeding adaptation: it drives the pointed muzzle and barbels into clean sand to taste out buried insect larvae, small crustaceans, worms and other invertebrates along with organic detritus, expelling the sifted sand through the gill openings as it works. Living on current-swept sand below rapids, it is well placed to take small drifting and benthic invertebrates. In the aquarium it accepts the usual cory diet — sinking pellets and wafers, frozen bloodworm and brine shrimp, and other small foods that reach the bottom — and should be offered a varied menu rather than left on leftovers.
Mating
Spawning behaviour has not been described specifically for this species, and the account below is the standard, well-studied pattern of the genus. Corys are egg-laying shoalers without a pair bond: a receptive female cleans a spawning surface, the group becomes active, and a male takes up the characteristic 'T-position' at right angles to the female's head. She appears to take milt into her mouth, the sperm passing quickly through her gut to fertilise the few eggs she clasps in a basket of her pelvic fins before pressing them onto the cleaned site. The process repeats, a few eggs at a time, over the course of a spawning.
Breeding
There is no published captive-breeding report for Corydoras approuaguensis. As a long-snouted species from clear, fast, well-oxygenated Guiana Shield rivers it is likely to be more demanding than the easy short-nosed corys, and success would probably depend on reproducing those conditions — clean, cool, gently to moderately flowing soft water over fine sand. By analogy with the genus, a cool rain-simulating water change would be the natural trigger, the adhesive eggs would be laid on firm surfaces with no parental care, and the adults would eat their own spawn unless eggs or parents were separated. Fish in the trade are wild-caught from French Guiana rather than commercially bred.
In the aquarium
Corydoras approuaguensis reaches the hobby only as an occasional wild import from French Guiana, of most interest to keepers who like the long-snouted Guianese corys. It is a peaceful shoaling fish and must be kept in a group of six or more; in ones and twos it becomes shy and stressed. Give the group a tank with a large footprint and, above all, a bed of soft sand — long-nosed corys are especially prone to barbel erosion on sharp or coarse gravel, which leaves them blunt-faced and unable to feed.
Its river-beach origins mean it wants clean, well-oxygenated water with a brisk gentle current, warm but not hot (around 72–79 °F), and diligent maintenance; a current from the filter return suits it better than dead-still water. Furnish with wood, smooth rock and an open sand area for foraging. It is entirely peaceful and belongs with calm, similarly sized community fish such as small tetras and pencilfish. The usual cory cautions apply — the fin spines snag in nets, so move it in a cup, and a badly stressed cory can release a skin toxin that may kill a whole group within the small volume of a transport bag.
Conservation
Corydoras approuaguensis was assessed by the IUCN in 2021 and listed as Least Concern. It is restricted to the single Approuague basin, but within that river it is reported as locally abundant, and the Approuague drains relatively well-preserved, thinly populated forest with no identified range-wide threat. The principal risk to clear-water, sand-dwelling fishes of this kind in the Guianas is gold mining — both the legal and the widespread illegal small-scale workings load the rivers with sediment and mercury and smother exactly the swept-sand habitats this species depends on. A Least Concern listing is therefore reassuring but not a reason for complacency about a basin-endemic clear-water specialist.