Taxonomy & naming
Microglanis parahybae was described by the Austrian ichthyologist Franz Steindachner in 1880. It belongs to the genus Microglanis, a group of small South American catfishes now placed in the family Pseudopimelodidae (the "false pimelodids" or dwarf/bumblebee catfishes), a family split out from the long-whiskered Pimelodidae as taxonomy of the group was revised. The species epithet parahybae refers to the Paraíba (historically spelled "Parahyba") do Sul river, the type locality and the drainage to which the species is endemic.
Microglanis parahybae is part of a species complex within the genus and is known to occur alongside a close relative, M. pleriqueater, in the neighbouring Macabu River basin of eastern Brazil; the two are distinguished by fine details of colour pattern and pectoral-spine serration. It should not be confused with Steindachneridion parahybae, an unrelated and much larger pimelodid from the same river system that carries a similar-sounding name but sits in a different genus entirely and is Critically Endangered.
Morphology
This is a genuinely small catfish: FishBase records a maximum size of about 3 in standard length, and it should be kept to that expectation rather than assumed to grow into anything larger. The body is light brown with a pattern of darker brown saddle-like blotches across the back, a light oval spot beneath the base of the dorsal-fin spine, and a caudal fin whose upper lobe is more developed than the lower.
Like other pseudopimelodids and pimelodids, Microglanis parahybae has small eyes, short barbels around the mouth, and completely scaleless, naked skin — a trait that matters for medication dosing (see "In the aquarium"). The pectoral fins carry a stiff, serrated spine that can lock in the erect position; no venom has been documented in the species, but the spine can still snag a net and should be handled with a container rather than netted by hand.
Habitat
Microglanis parahybae is endemic to the Paraíba do Sul river basin in eastern Brazil, a coastal drainage running through the states of São Paulo, Rio de Janeiro and Minas Gerais. As a demersal species it lives on or near the riverbed, sheltering by day and emerging to forage after dark.
Water in its native range is recorded as neutral to slightly alkaline, with a pH of roughly 6.2–7.8, and warm-temperate to tropical, with temperatures around 70–79 °F — cooler than many classic Amazonian community fish. This is not a soft, acidic blackwater species; keepers should match the moderate pH and moderate temperature range documented for the species rather than defaulting to blackwater conditions.
Feeding
Microglanis parahybae is a nocturnal, benthic omnivore. In the wild it forages along the bottom, taking small invertebrates, detritus and whatever edible material it encounters, mostly under cover of darkness.
In the aquarium it is not a fussy feeder and will take standard sinking foods — pellets, frozen bloodworm and brine shrimp, and other prepared foods — once it has settled in. Because it is most active after lights-out, offering food in the evening or after the tank lights go off gives it a fair chance against faster, more visible tankmates.
Mating
No courtship or spawning behaviour has been documented for Microglanis parahybae in the wild or in the aquarium. Hobby sources note that, by analogy with related small pseudopimelodids, soft and slightly acidic water is theorised to favour spawning, but this has not actually been tested or achieved for this species specifically.
Breeding
Breeding of Microglanis parahybae has not been documented in the aquarium. Related Microglanis species are also rarely if ever bred by hobbyists, and there is no confirmed record of a home spawning for this species. Anyone acquiring this fish should assume wild-collected or commercially propagated stock rather than expecting to breed it, and should treat any claim of captive-bred fry with appropriate scepticism until better documented.
In the aquarium
At a genuine maximum of about 3 in, Microglanis parahybae is one of the more modestly sized catfish in the trade and does not present the size trap that so many larger catfish do — but its needs are still specific. It is a scaleless catfish, so it is more sensitive than scaled fish to copper-based medications and many treatments; dose conservatively, often at reduced strength, and remove it before treating a tank aggressively. Its pectoral spines can lock and snag a net, so it is best transferred in a container rather than chased with a net.
Provide plenty of cover — smooth rockwork, driftwood, leaf litter or dense planting — since this is a nocturnal hider that spends daylight hours tucked away and may only become confident enough to emerge at feeding time once well acclimated. Keep water parameters within the documented range (pH roughly 6.2–7.8, temperature 70–79 °F) and avoid rough-textured or overly bright, sparse setups that leave it nowhere to retreat. Tankmates should be peaceful and not large enough to see this small catfish as food.
Conservation
Microglanis parahybae has not been evaluated by the IUCN Red List (Not Evaluated). As a habitat specialist restricted to the Paraíba do Sul basin — a heavily populated, industrialised and agriculturally developed drainage in eastern Brazil — it is reasonable to assume some exposure to water-quality pressures typical of that river system, but no dedicated population assessment or conservation status is currently available for this species. This is worth remembering when compared with the unrelated but similarly named Steindachneridion parahybae from the same river, which is Critically Endangered; the two should not be conflated when discussing conservation status.