Taxonomy & naming
Corydoras paragua was described by Joachim Knaack in 2004, in the Dresden museum series Zoologische Abhandlungen, from specimens collected at the mouth of the Río Paraguá on the upper Iténez (Guaporé) in Departamento Santa Cruz, Bolivia. The epithet is simply the name of that river. It was placed, as nearly all such catfishes then were, in the genus Corydoras (family Callichthyidae, subfamily Corydoradinae).
The 2024 revision of the subfamily by Dias, Tencatt and colleagues broke the oversized genus Corydoras into several genera on phylogenetic grounds, and the Paragua cory falls within the resurrected genus Hoplisoma — the large lineage that holds the majority of the small, short-snouted 'corys.' Its current valid combination is therefore Hoplisoma paragua, and FishBase already lists it under that name. The aquarium world still uses 'Corydoras paragua,' so we keep that as the heading while recording the new placement. Catalog of Fishes treats paragua Knaack, 2004 as a valid species; we follow that authority.
Morphology
This is a small, short-snouted cory, reaching only about 1.5 in in standard length — well within the 'dwarf' size class — with the deep, compact body and twin rows of overlapping bony scutes shared by the whole subfamily. The head is rounded and bears three pairs of barbels around the downturned mouth, and the dorsal and pectoral fins carry the usual stiff leading spines.
Detailed colour notes for the species are sparse in the hobby literature; like its small Hoplisoma relatives it is a patterned fish rather than a plain one, with dark markings on a paler ground. As in essentially all corys, females grow larger and rounder than males — a difference seen most clearly from above — while mature males tend to have more pointed fins. Its very small adult size is the most useful single field character separating it from the many larger corys of the same region.
Habitat
The Paragua cory is known from the Río Paraguá, a northwestern tributary in the Iténez (Guaporé) system of lowland eastern Bolivia; the Guaporé in turn drains into the Mamoré and the upper Madeira, part of the greater Amazon basin. The type material came from the river-mouth area of the Paraguá, and Planet Catfish maps the species across the Guaporé–Mamoré–Madeira lowlands.
These are warm, lowland tropical waters — slow streams, river margins and floodplain pools over sand and leaf litter — typically soft and acidic to near-neutral. No formal water-chemistry envelope has been published for the species, so the husbandry values given here are reasonable figures for a small lowland Amazon-drainage cory rather than measured field data. Like all corydoradines it can supplement gill respiration by gulping air at the surface, an adaptation for the warm, oxygen-poor pools of the dry season.
Feeding
There is no published wild-diet study for Corydoras paragua, but it is a typical benthic corydoradine and forages exactly as its relatives do: nosing and sifting through soft substrate with its barbels to extract small invertebrates, larvae, microcrustacea, worms and organic detritus, and passing cleaned sediment out through the gills. In the aquarium it accepts the full range of sinking prepared foods — micro-pellets, tablets and crushed flake — along with small live and frozen foods such as baby brine shrimp, Daphnia, microworm and finely chopped bloodworm, which suit its small mouth and are useful for conditioning.
Mating
No spawning of this species has been documented, but corydoradine courtship is stereotyped enough to describe by analogy. They are egg-laying shoalers without a pair bond: a ripe female cleans a site, the group becomes excited, and a male assumes the 'T-position' across the front of her head. Milt is thought to pass quickly through the female's gut to fertilise the small number of eggs she cups in a basket of her pelvic fins, which she then presses onto the cleaned surface — repeating the cycle a few eggs at a time until the clutch is laid.
Breeding
There is no breeding report for the Paragua cory, registered or published, so any account is by extension from its small Hoplisoma relatives rather than from records of this fish. Small corys of this type are generally bred by conditioning a group well and triggering spawning with a cool, large water change that mimics the rains; they scatter adhesive eggs onto plants, wood and glass and give no parental care, so the eggs or the adults must be separated to stop the parents eating them. The fry are correspondingly tiny and need very fine first foods. Until first-hand reports exist, the specifics for this species remain unknown.
In the aquarium
C. paragua is an uncommon import rather than a staple, but as a small, peaceful Hoplisoma it is undemanding where its basic needs are met. It is a shoaling fish and should be kept in groups of six or more; kept singly or in pairs it is shy and inactive. Being small, it is well suited to modest, well-planted tanks, and a soft sand substrate is effectively a requirement — corys sift constantly, and sharp or chipped gravel wears and infects their barbels.
It wants warm, clean, well-oxygenated water with gentle flow and regular changes, and being a small-mouthed fish it does best where food actually reaches the bottom rather than being intercepted by larger tankmates. It is utterly peaceful and an ideal companion for small tetras, pencilfish, dwarf cichlids and similar calm community fish, and should never be housed with anything large enough to bully or eat it. As with all corys, net the fish in a cup rather than a mesh net to avoid snagging the fin spines, and move them carefully, since a badly stressed cory can release skin toxins that are dangerous in the confined volume of a bag.
Conservation
Corydoras paragua has not been assessed by the IUCN and carries no Red List category, so its conservation status is formally unknown. It appears to be a range-restricted species of the Río Paraguá and the wider Guaporé–Iténez lowlands. That region is still relatively intact compared with much of South America, but a narrowly distributed lowland fish is inherently more exposed to local pressures — deforestation, agriculture and changes to seasonal flooding — than the widespread corys of the trade. A formal assessment would be needed to say anything definite about its status.