Taxonomy & naming
Hoplisoma tenebrosum was formally described in 2025 by Tencatt, Ohara, Carvalho, Grant and Britto, in the journal Neotropical Ichthyology, in a paper that erected two new dark-patterned species from the rio Tapajós basin alongside a discussion of mesethmoid (snout-bone) morphology in the Corydoradinae. Long known to aquarists under a CW collection number, it received its formal name only after the genus had been revised.
That revision matters to the name. In 2024 Dias, Tencatt and colleagues split the old over-large genus Corydoras among several resurrected genera, and the short-snouted 'classic' corys went into Hoplisoma. Because tenebrosus was described after the revision, its authors placed it directly in that genus, so its original and current combination is Hoplisoma tenebrosum (the neuter genus requires the neuter ending of the adjective). The hobby will continue to encounter it written as 'Hoplisoma tenebrosum', so we keep that heading while noting the formal name. The epithet, from the Latin tenebrosus, 'dark, shadowy, gloomy', refers to the species' heavy dark markings.
This fish was long listed as Corydoras tenebrosus; Eschmeyer's Catalog of Fishes places the species in Hoplisoma, and the current combination Hoplisoma tenebrosum is followed here.
Morphology
This is a small, short-snouted cory; the type series runs to roughly 2 in in standard length (the largest measured paratype around 2.2 in SL). It has the standard armoured build — a deep, flat-bellied body clad in two overlapping rows of bony scutes meeting in a dorsal ridge, a blunt head, and three pairs of barbels around the downturned mouth.
Its colour is what gives it its name. The body carries a heavy, dark pattern: two or three longitudinal dark-brown to black stripes running along the flanks, and a large, smoothly arched dark patch across the head that masks the eye region — a sombre, shadowed look that the epithet tenebrosus ('dark') captures. The dorsal, pectoral and adipose fins each bear a stiff leading spine. As in most corys, females grow larger and rounder than males.
Habitat
Hoplisoma tenebrosum is known from the rio Tapajós basin within the greater rio Amazonas drainage, around Maués in Amazonas State, Brazil — the type locality is a forest stream (igarapé) system in that area, with a further record from another nearby igarapé. This is a restricted, recently documented distribution in the lowland rainforest of the central-southern Amazon.
It is a benthic fish of small, clear forest streams (igarapés) — shaded, soft-bottomed waters with sand, leaf litter and submerged wood. These are warm, soft, acidic blackwater-influenced streams, broadly in the 75–82 °F range with low pH and low hardness typical of Tapajós-basin forest waters. Like all corys it is a facultative air-breather, surfacing to gulp air and absorb oxygen through a vascularised hindgut. Specific measured water chemistry from the type locality is limited, so the aquarium figures below are conservative estimates consistent with its habitat.
Feeding
As a member of the genus, Hoplisoma tenebrosum is a benthic omnivore and detritivore. It works the bottom of its forest streams, burying its snout and barbels in sand and leaf litter to taste out small invertebrates, insect larvae, micro-crustaceans and organic detritus, expelling cleaned substrate through the gills. No diet study specific to this newly described species exists, but in captivity it would be expected to take the usual cory fare — sinking pellets, frozen bloodworm and brine shrimp and other small foods — and to need a varied diet rather than tankmates' leftovers.
Mating
Corys are egg-laying shoalers with no pair bond and a distinctive courtship. A ready female cleans a spawning site and the group becomes active; a male takes up the classic 'T-position' at right angles to her head, and she appears to take his milt into her mouth. Sperm is thought to pass rapidly through her gut to fertilise the few eggs held in a basket of her pelvic fins, which she presses onto the cleaned surface. The sequence repeats a few eggs at a time. No mating observations exist for this newly described species specifically, but it is expected to follow this group-wide pattern.
Breeding
There is no published aquarium breeding data for Hoplisoma tenebrosum — it is a 2025 description, still uncommon in the hobby. As a short-snouted Hoplisoma-group cory it would be expected to spawn in the manner of the genus: a cooler, large water change imitating the rainy season triggers a group skewed toward more males than females, adhesive eggs are laid in small batches on cleaned surfaces, and the eggs receive no parental care, with adults eating them unless breeders remove eggs or parents. Honest note: everything specific about its reproduction — clutch size, triggers, fry development — is presently undocumented.
In the aquarium
Hoplisoma tenebrosum is a new and uncommon species rather than a trade staple, and reliable husbandry experience is still accumulating. As with every cory it should be kept in a group of six or more; alone or in pairs it is stressed and reclusive. Give a group a footprint of at least 23.6 in, since bottom area matters more than height.
Substrate must be soft sand or very smooth fine sand, never sharp or coarse gravel, which erodes and infects the barbels. Coming from soft, acidic Tapajós-basin forest streams, it is best given warm (about 75–82 °F), soft, slightly acidic, well-filtered and well-oxygenated water with regular changes, ideally over a darker substrate with leaf litter and wood that suit a blackwater fish. It is peaceful and suits a quiet community of small Amazonian tetras and dwarf cichlids. As with any cory, net spines catch easily (use a cup), and — a point underscored by its close relative described in the same paper, which produces a notably toxic skin secretion — a distressed cory can release skin toxins that, in the confined volume of a transport bag, can kill the whole group. Handle and transport with real care.
Conservation
Hoplisoma tenebrosum has not been assessed by the IUCN Red List — it was described only in 2025, and no conservation evaluation has yet been published, so its status is Not Evaluated. Its known range is small, confined so far to a few forest streams of the rio Tapajós basin around Maués, and the describing authors flagged habitat loss in the region as a concern: the central-southern Amazon faces active pressure from deforestation, road-building, agriculture and mining. A narrowly distributed, newly described fish in a developing frontier is exactly the kind of species whose status needs prompt assessment, but at present the honest answer is that it is unassessed.