Taxonomy & naming
Hemidoras stenopeltis was described by the Austrian ichthyologist Rudolf Kner in 1855. It belongs to the family Doradidae, the thorny or talking catfishes of South America, a large group whose members are united by rows of bony lateral scutes and by the ability to produce sound using their pectoral spines and swim bladder. The genus Hemidoras sits within this family alongside other South American doradids historically shuffled between genera such as Doras, and the Catalog of Fishes (Eschmeyer, CAS) is the reference followed here for the valid combination Hemidoras stenopeltis.
As with many older Doradidae descriptions, species in this group were at times placed under broader genera such as Doras before the modern generic boundaries of Hemidoras were settled; the current placement in Hemidoras is retained here.
Morphology
Hemidoras stenopeltis reaches a maximum recorded size of about 7.5 in standard length, with adults topping out around 86.5 g in weight (FishBase) — a modestly sized doradid, though still a fish that needs real swimming room, not a nano-tank resident. Like other thorny catfishes it lacks true scales; instead a single row of bony, keeled lateral plates, each often bearing small hooks or spines, runs along the flank from head to tail, giving the family its "thorny catfish" name.
The body is elongated and somewhat compressed, with a moderately long-based dorsal fin and an adipose fin behind it. Doradids including Hemidoras carry stiff, serrated, LOCKING spines at the leading edge of the dorsal and pectoral fins that can be erected and held rigid — these snag readily in aquarium nets and can jab an unwary hand, so this fish is best scooped and moved in a container rather than netted. The skin, though plated, is naked of true scales and is correspondingly sensitive to certain medications, as in loaches, puffers and eels.
Habitat
The species is native to the Amazon basin, with records from Brazil, Colombia and Peru. It is a freshwater, demersal fish associated with slowly flowing and stationary water areas — backwaters, flooded forest margins and quiet channels rather than fast, well-oxygenated rapids.
Reported aquarium water parameters are a temperature of roughly 72–79 °F, pH around 6.0–7.8 and hardness of about 5–20 dH (PlanetCatfish), placing it in soft-to-moderately-hard, mildly acidic-to-neutral tropical water typical of much of the Amazon's calmer habitats. It is not a demanding fish about exact chemistry within that range, but stability and clean water matter more than chasing a precise number.
Feeding
Hemidoras stenopeltis is a nocturnal benthic omnivore. By day it rests hidden under roots, leaf litter and vegetation; after dark it emerges to forage over the bottom for invertebrates, detritus and other small food items typical of the doradid diet.
In the aquarium it readily accepts sinking pellets, frozen foods and other prepared diets. Because it is most active at night, feeding after the lights go out — or offering a sinking meal that survives to lights-out — helps ensure it is not out-competed by more visible, daytime tankmates.
Mating
Specific courtship and spawning behaviour for Hemidoras stenopeltis is not documented in the available sources; breeding data for this species is sparse. Among the thorny catfishes generally, reproductive strategies vary by genus and are not uniform across Doradidae, so no mode should be assumed for this species without direct evidence.
Breeding
There is no confirmed record of Hemidoras stenopeltis being bred in the home aquarium, and detailed breeding behaviour was not found in the sources consulted. It is best treated, honestly, as a species that is not established as captive-bred at the hobbyist level — any specimens in the trade should be assumed wild-collected unless stated otherwise. Keepers should not expect to replicate spawning without further published information on this particular species.
In the aquarium
Size this fish for its real adult length of close to 8 in — a spacious tank with a long footprint suits it far better than a small community setup, and the size trap of assuming a juvenile doradid will stay small is worth avoiding here as with any catfish. Provide a dark, sandy substrate along with driftwood, tubes or rock formations to give daytime hiding places, since this is a nocturnal fish that shelters under cover until evening.
Because it is scaleless and plated rather than true-scaled, treat it as medication-sensitive: dose copper-based treatments and many other medications conservatively, as with loaches, puffers and eels. Its dorsal and pectoral spines lock rigid and are serrated, so use a container rather than a net when moving it to avoid tangling the fish or injuring your hands. Keep it with robust tankmates that will not be intimidated after dark, and expect to see it most active once the lights go down.
Conservation
Hemidoras stenopeltis has not been formally assessed by the IUCN Red List and is listed as Not Evaluated (NE). This is common among Amazon-basin doradids that are not major targets of the food or ornamental trade at scale; the absence of an assessment reflects a lack of dedicated evaluation rather than any known population concern.
Its range across the Amazon basin in Brazil, Colombia and Peru spans a vast area, and no specific threats to the species have been documented in the sources reviewed. As with many lesser-known Amazonian fishes, habitat pressures on the wider basin — deforestation, water-quality change and localized fishing — are the general concerns relevant to its ecoregion even without a species-specific assessment.