Taxonomy & naming
Hoplosternum magdalenae was described by Carl H. Eigenmann in 1913, taking its species epithet from the Magdalena River basin of Colombia where it was first collected. It belongs to the family Callichthyidae, the armoured catfishes, in the subfamily Callichthyinae alongside Callichthys, Dianema and Megalechis — the larger-bodied cousins of the familiar Corydoras.
The genus Hoplosternum has had a tangled taxonomic history typical of Siluriformes, with species shuffled between Callichthys, Hoplosternum and (for the related "Megalechis" species) back and forth over the decades as authors revised the subfamily. The Catalog of Fishes currently treats Hoplosternum magdalenae as the valid combination, and that is the name used here; older literature and some aquarium sources may still list it under a different arrangement.
Morphology
Like all callichthyids, Hoplosternum magdalenae is armoured rather than scaled: two overlapping rows of bony plates (scutes) run down each flank from head to tail, a defence that also means the fish lacks the fine, easily damaged scales of a typical bony fish. The body is elongated and moderately robust, with a flattened underside suited to a bottom-dwelling life, a blunt head, and paired barbels used to feel out food. The common name comes from a dark longitudinal stripe that runs along the body, distinguishing it from plainer relatives.
FishBase records a maximum size of about 4.5 in standard length — a genuinely manageable adult size for this species, though keepers should still plan for a full-grown fish rather than the smaller juvenile usually sold. As in other armoured catfish, the stiff pectoral and dorsal spines can be locked erect and are mildly serrated; they catch easily in an aquarium net.
Habitat
The species is native to northwestern South America, recorded from the Magdalena and Sinú River basins of Colombia and the Lake Maracaibo basin of Venezuela. These are warm, seasonally fluctuating lowland river systems, and callichthyids of this group are typically found in slow water, floodplain pools, swamps and vegetated margins rather than fast current — habitats that can become oxygen-poor as they shrink in the dry season.
That oxygen-poor habitat is exactly why Hoplosternum magdalenae is an obligate air-breather: it must periodically rise to gulp air at the surface, using a vascularised section of its gut to extract oxygen, and cannot survive on gill respiration alone even in well-aerated water. In the aquarium this means the water surface must always be accessible — never seal a tank so tightly that the fish cannot reach air.
Feeding
Hoplosternum magdalenae is a nocturnal benthic omnivore, foraging over the substrate mainly after dark for invertebrates, detritus and other small food items washed or settled onto the bottom. In the aquarium it is unfussy and will take sinking pellets and flake along with frozen foods such as bloodworm and brine shrimp, plus blackworms.
Because it is most active at night and has poor eyesight — relying on its barbels to find food by touch rather than sight — it does best when some food is offered after the lights go out, so it is not consistently out-competed by more visually oriented daytime tankmates.
Mating
Courtship in this species follows the bubble-nest pattern shared by Hoplosternum and its callichthyid relatives, unlike the open-water egg-scattering typical of many other catfish. The male begins building a raft of mucus-coated bubbles at the water's surface, often anchored under a broad leaf or floating cover, working the nest into a stable pad that will hold the coming clutch above the water.
A cooler water change of a few degrees is commonly reported as a breeding trigger, mimicking the seasonal rains that refresh floodplain habitats in the wild. Males become notably more aggressive and territorial around the nest site once conditions are right and courtship is underway, so a spawning setup should give a pair or trio room to establish territory away from other tankmates.
Breeding
Hoplosternum magdalenae is a genuine bubble-nest builder: the male constructs the floating raft described above, the eggs are deposited into it during spawning, and the male alone then guards and tends the nest, fanning and defending it until the fry hatch and disperse. This places the species among the minority of catfish in this atlas that are realistically home-breedable, rather than farm- or hormone-spawned at commercial scale.
A spawning tank with a stable, well-covered leaf or floating material to anchor the nest, soft-to-moderate water, and a cooling water change to cue spawning is the standard approach reported by breeders. Once the male is guarding a nest he should not be disturbed or removed, since he is the sole source of parental care for the clutch; the female typically takes no further part after laying.
In the aquarium
At a maximum recorded size of roughly 4.5 in, Hoplosternum magdalenae suits an aquarium of modest size by catfish standards, but keepers should still size the tank to the adult rather than the juvenile, and provide a soft substrate for the fish to root and dig in. As an obligate air-breather it needs unobstructed access to the surface, so avoid tight-fitting covers or a permanently high water line with no air gap.
Being scaleless and plate-armoured rather than scaled, it is medication-sensitive in the way most catfish are — dose copper-based and other treatments conservatively. Its locking pectoral and dorsal spines tangle easily in a net and can jab the handler, so it is best scooped and moved in a container rather than chased with a net. Water tolerance is broad — sources report a pH range from about 5.5 to 8.5 across soft to very hard water — making it forgiving of typical tap-water chemistry. It is a peaceful bottom-dweller and a reasonable community fish for tankmates that will not harass a slow-moving, nocturnal forager.
Conservation
The IUCN Red List assesses Hoplosternum magdalenae as Least Concern. It occupies a fairly wide native range across the Magdalena, Sinú and Maracaibo basins and is not currently considered at risk at the species level.
As with other floodplain fish of these basins, the longer-term pressures are habitat-scale rather than direct exploitation: wetland drainage, water pollution and hydrological changes to the Magdalena and Maracaibo systems from agriculture and development are the relevant concerns for the wider ecosystem this species depends on, even though the species itself is not flagged as threatened.