Taxonomy & naming
Lepthoplosternum beni was described by Roberto E. Reis in 1997, part of a revision that split the older, broadly defined genus Hoplosternum into several narrower genera, including Lepthoplosternum. Older aquarium and hobby literature may still refer to fish of this genus under the now-obsolete Hoplosternum combination; the Catalog of Fishes treats Lepthoplosternum beni as the currently valid name, in the family Callichthyidae.
The genus name Lepthoplosternum combines Greek roots referring to a slender armored breastplate, describing the narrow, plated body typical of the genus. The species epithet beni refers to the Beni Department of Bolivia and the Beni River, part of the type locality in the upper Madeira River drainage.
Morphology
Like all callichthyids, Lepthoplosternum beni has no true scales. Instead, two overlapping rows of bony plates (scutes) run the length of each flank, giving the body a segmented, armored look. This is a genuinely small species: adults reach only about 2 in standard length, among the smallest fish in the armored-catfish group, and this real adult size should be taken at face value rather than assumed to grow further.
The body is elongate with a slightly arched back, a small ventral mouth flanked by short barbels used to grub through sediment, and the paired dorsal and pectoral fins each carry a stiff, serrated spine that locks erect. As with other scaleless, plated catfish, these spines can snag a net and jab bare skin, so the fish is best scooped and moved in a container rather than netted.
Habitat
The species is native to the upper Madeira River basin in the Beni region of Bolivia and adjacent Peru, part of the greater Amazon drainage in western South America. It occupies the slow-flowing, vegetated margins, floodplain pools and backwaters typical of small Amazonian tributaries, habitats prone to seasonal flooding and periods of low dissolved oxygen.
Like other callichthyids, L. beni is an obligate air-breather, rising to gulp atmospheric air at the surface to supplement gill respiration — an adaptation that lets it survive in the oxygen-poor, still water where it lives. Reported water conditions for the genus run warm and only mildly acidic to neutral rather than the deeply tannin-stained blackwater sometimes assumed for small Amazonian catfish; a related species, L. pectorale, is kept at roughly 68–72 °F and pH 6–8, and similarly moderate parameters are the sensible baseline for L. beni given its small size.
Feeding
Lepthoplosternum beni is a nocturnal benthic omnivore, foraging over the substrate mainly after dark for small invertebrates, detritus and organic matter sifted through its barbelled mouth. It is not a picky specialist.
In the aquarium it readily takes sinking pellets, wafers and frozen foods such as bloodworm and brine shrimp, along with most prepared foods. Because it feeds primarily at night, offering food after the lights go out helps ensure a shy, small fish like this one is not out-competed by more active tankmates.
Mating
As in other armored callichthyids, courtship in Lepthoplosternum beni centres on the male's construction of a floating bubble-nest rather than any open-water chase or substrate-clearing display. The male blows a raft of mucus-coated bubbles at the surface, often anchored beneath a broad leaf or floating plant, and entices a ripe female to the nest site.
During spawning the pair positions close together and the female deposits eggs, which are fertilised and worked into the bubble-raft. This internal-fertilisation-free, bubble-nest strategy is one of the more reliably observed and reproducible breeding behaviours among the smaller catfish groups, and it is what makes armored callichthyids like this one genuinely approachable for a home breeding attempt.
Breeding
Lepthoplosternum beni is a bubble-nest builder: the male constructs and guards a floating raft of bubbles at the surface, the eggs are placed into it, and the male alone tends and defends the nest until the fry hatch and disperse. This places it among the minority of catfish covered here that are genuinely breedable in a home aquarium without hormone induction or farm-scale infrastructure.
A well-fed, conditioned pair or small group in soft, slightly warmed water with floating cover to anchor the nest is the standard approach used for its callichthyid relatives. Because the male provides all parental care, he should not be removed once eggs are laid; the female can be pulled after spawning to avoid interference. Given the tiny adult size of this species, expect correspondingly small clutches and fry.
In the aquarium
At only about 2 in, Lepthoplosternum beni is comfortable in a modestly sized aquarium and does not pose the size-trap risk of many larger catfish — but it should still be kept in a group, on fine, soft substrate that will not abrade its barbels, with plenty of leaf litter or floating cover to shelter it by day and support a bubble-nest at night. As an obligate air-breather it needs unobstructed access to the surface at all times.
Being scaleless and plated rather than scaled, it is medication-sensitive: dose copper-based and other treatments conservatively, well below levels safe for scaled fish. Its dorsal and pectoral spines lock and can snag a net, so move it in a cup or container instead. It is peaceful with similarly small tankmates and, like its relatives, will benefit from feeding after dark given its nocturnal habits.
Conservation
The IUCN Red List assesses Lepthoplosternum beni as Least Concern. It has a restricted native range centred on the upper Madeira basin in Bolivia and Peru, but is not currently reported as facing significant range-wide pressure.
As with many small, poorly studied Amazonian tributary fish, localized threats such as habitat alteration, water quality changes and deforestation in the Beni region are the main long-term concerns even where the overall status remains favourable. The aquarium trade for this species is small and not considered a major driver of wild population pressure.