Taxonomy & naming
Batrochoglanis melanurus was described by Osvaldo Oyakawa and Suzana Pavanelli in 2005, part of the modern revision that clarified the small-bodied pseudopimelodid catfishes of the Batrochoglanis–Microglanis complex. It sits in the family Pseudopimelodidae — the bumblebee catfishes — within the subfamily Batrochoglaninae, and the Catalog of Fishes treats Batrochoglanis melanurus as the currently valid name with no need for a genus correction.
The genus name Batrochoglanis derives from Greek batrachos (frog) and glanis (a catfish), an old allusion to the broad, flattened, almost frog-like head shared by species in this genus. The species epithet melanurus combines melan- (black) with -ourus (tailed), "black-tailed", describing the fish's most distinctive feature: a caudal fin that is a homogeneous dark brown rather than banded or spotted, which is what separates it from its closest congeners under the microscope and in the field.
Morphology
Batrochoglanis melanurus reaches a modest maximum size of about 5.5 in standard length, making it one of the smaller pseudopimelodids and well within reach of a home aquarium — though, as with any catfish, the real adult size should be planned for from the start rather than assumed away. Like its relatives it has the broad, dorsoventrally flattened head typical of the genus, a stout body tapering to the tail, and long barbels used to feel out food and cover in low light.
The skin is scaleless, as in the great majority of catfishes, which makes the species more sensitive than scaled fish to copper-based medications and many standard treatments — conservative, often half-strength dosing is the safer default. The dorsal and pectoral fins carry the stiff, serrated, locking spines typical of catfish; these lock rigid when the fish is alarmed, tangle readily in aquarium nets, and can jab the keeper, so the fish is best moved in a container rather than netted. The namesake feature is the tail: a uniform dark-brown caudal fin without the paler markings or banding seen in related species.
Habitat
The species is known only from its type locality, the córrego Cancela, a small stream tributary to the rio Cuiabá within the greater rio Paraguai (Paraguay River) basin, in the State of Mato Grosso, Brazil. This narrow known range — a single named stream — is typical of many small pseudopimelodid catfishes, which are easy to overlook and likely under-recorded across the wider basin.
Detailed water chemistry data for the type locality has not been captured here, and it should not be assumed to match the soft, acidic blackwater conditions of Amazonian forest streams; the rio Paraguai basin includes a range of clearwater and seasonally flooded habitats. Keepers should provide warm, well-oxygenated, moderately soft-to-neutral water and treat any more specific pH or hardness figures as provisional pending further data.
Feeding
Batrochoglanis melanurus is a nocturnal benthic omnivore, foraging over the stream bed mostly after dark for small invertebrates, detritus, and other opportunistic prey — the general pattern documented across the genus and the wider Pseudopimelodidae. It is not a specialised hunter of fish at this size, but like most catfish will take anything small enough to fit in its mouth.
In the aquarium it takes protein-rich sinking pellets, frozen bloodworm, and small live foods readily. Because it feeds mainly at night, offering food after the lights go out ensures it gets a fair share rather than being out-competed by diurnal tankmates.
Mating
No courtship or spawning behaviour has been documented for Batrochoglanis melanurus in the cache material available here. Breeding accounts for the wider Pseudopimelodidae are sparse, and nothing specific to this species' mating behaviour in the wild or in captivity is confirmed — this is honestly unknown rather than assumed.
Breeding
Breeding of Batrochoglanis melanurus in the aquarium is essentially undocumented; hobbyist sources describe it as largely unknown in home tanks, with any commercial-scale propagation relying on hormone induction rather than natural spawning behaviour being replicated by aquarists. This mirrors the pattern seen across many small pseudopimelodid and heptapterid catfishes, which are wild-collected for the trade rather than captive-bred.
Prospective keepers should not expect to breed this species at home; if it does spawn, no parental-care pattern has been recorded to guide expectations, and any reports should be treated as noteworthy rather than routine.
In the aquarium
At a modest maximum of roughly 5.5 in, Batrochoglanis melanurus is manageable in a well-planned tank, but its full adult size — not a juvenile's — should set the stocking plan; a single specimen still needs a real footprint of floor space with dense cover, since it is nocturnal and shy, hiding through the day and emerging to forage after dark. Caves, driftwood tangles, and plants give it the security it needs; dim lighting suits it best.
Because it is scaleless, treat it as medication-sensitive: dose copper-based and other standard treatments conservatively, often at half strength, as is standard practice for naked-skinned catfish. Its dorsal and pectoral spines lock and can snag a net or jab bare skin, so move it in a cup or container rather than chasing it with a net. It is reported as peaceful toward tankmates it cannot eat, making it a workable, if under-the-radar, addition to a South American community aquarium furnished for a nocturnal bottom-dweller.
Conservation
The IUCN Red List assesses Batrochoglanis melanurus as Least Concern, with the assessment dated 7 November 2018. That listing sits somewhat uneasily alongside the fact that the species is known only from a single locality — the córrego Cancela in the rio Cuiabá drainage of the rio Paraguai basin — a narrow known range that is more a reflection of limited survey effort for small pseudopimelodid catfishes than confirmed abundance across the basin.
There is no indication in the available sources that the species is targeted for the aquarium trade at any scale, and no specific threats have been documented. As with many small, poorly surveyed Neotropical catfishes, its conservation picture would benefit from further field work across the wider rio Paraguai system rather than reliance on a single-site record.