Taxonomy & naming
Microglanis malabarbai was described by Vinicius A. Bertaco and Alexandre R. Cardoso in 2005. It belongs to the family Pseudopimelodidae, the bumblebee and dwarf marbled catfishes, a group that was long lumped into Pimelodidae before being recognised as its own family; older literature may therefore still file Microglanis species under Pimelodidae. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) treats Microglanis malabarbai as the valid name, with no synonyms in wide use.
The genus Microglanis combines Greek mikros, "small", with glanis, an old name for a catfish — "small catfish", a fitting label for a genus whose members rarely exceed a few centimetres. The species epithet malabarbai honours a person (a common pattern in the many Bertaco-authored descriptions of southern Brazilian fishes from this period); the type locality is the Rio Ijuí, a tributary of the middle Rio Uruguay.
Morphology
Like other pseudopimelodids, Microglanis malabarbai has a stout, slightly flattened head, a short and deep body tapering to the tail, and long, sensitive barbels used to find food in low light or murky water. The skin is naked — Pseudopimelodidae, like the true pimelodids, have no scales — and the dorsal and pectoral fins carry stiff spines that can be locked erect.
The recorded maximum size is only about 2 in standard length, making this one of the smallest catfish in the atlas and a genuine dwarf even within the already-small genus Microglanis. Colouration is the classic "dwarf marbled catfish" pattern: mottled dark-brown and pale markings over the body, and a caudal fin that is almost completely black except for a narrow white band crossing it — a useful field mark separating it from its close relative M. garavelloi.
Habitat
This species is endemic to the Rio Ijuí, a tributary of the middle Rio Uruguay in Rio Grande do Sul, southern Brazil, and is not known to occur anywhere else. It is a warm tropical-to-subtropical freshwater fish of a South American coastal-drainage river system, in keeping with the wider distribution of Microglanis across the Paraná–Uruguay–Paraguay basins.
The cache and available literature do not report specific temperature or pH figures for the Rio Ijuí population, and none should be invented here — the species should be treated as a moderate, subtropical South American river fish typical of the middle Uruguay drainage rather than assigned soft blackwater or hard alkaline conditions without direct evidence.
Feeding
As with other small pseudopimelodids and Microglanis species generally, M. malabarbai is best understood as a nocturnal benthic micro-predator and omnivore, sheltering by day and foraging over the bottom after dark for small invertebrates, insect larvae and detritus.
Specific dietary data for this species is not documented in the sources reviewed here. In an aquarium setting, small sinking pellets, frozen foods (bloodworm, brine shrimp, chopped mysis) and other prepared foods sized for a roughly 2 in fish would suit its build, offered after lights-out so a shy, nocturnal cat is not out-competed by more active tankmates.
Mating
No description of courtship or spawning behaviour for Microglanis malabarbai has been documented in the sources reviewed. PlanetCatfish notes that breeding in captivity for closely related dwarf marbled catfishes is rare and poorly documented, and that pattern almost certainly extends to this species as well.
Breeding
Breeding has not been reported in the aquarium for Microglanis malabarbai, and no wild reproductive data is available from the sources consulted. This is honestly a gap rather than a settled account: unlike the bubble-nesting callichthyids or the internally-fertilising driftwood cats, small pseudopimelodids like Microglanis have no well-documented home-breeding record, and nothing here should be assumed about parental care, egg placement or spawning triggers. Anyone attempting it would be working largely from scratch.
In the aquarium
The real adult size here is small — about 2 in — so this is one of the very few catfish in the atlas where the usual "size trap" warning runs the other way: it will not outgrow a modest aquarium, but its small size means it is easily out-competed or even eaten by larger tankmates, and needs company sized to match. Provide fine sand or smooth gravel, plenty of leaf litter, wood and other cover, since it is a shy, nocturnal fish that hides by day and forages after dark.
It is scaleless, like other pseudopimelodids, so it carries the same medication sensitivity as loaches, puffers and eels — dose copper-based treatments and many general medications conservatively. It also bears small locking dorsal and pectoral spines typical of the family; move it in a container rather than a net to avoid tangling and injury to both fish and keeper. Given how little is documented about this species specifically, keepers should treat husbandry notes for the wider Microglanis/Pseudopimelodidae group as a starting point rather than a confirmed protocol.
Conservation
The IUCN Red List assesses Microglanis malabarbai as Near Threatened. The species is known only from the Rio Ijuí, a single tributary of the middle Rio Uruguay in Rio Grande do Sul, Brazil, which makes its entire global population vulnerable to any localised habitat change, pollution or damming within that one drainage.
Because it has such a restricted range and is not established in the aquarium trade, its conservation outlook is tied directly to the health of the Rio Ijuí itself rather than to collection pressure. There is no indication in the sources reviewed that this species is commercially traded or wild-collected for the hobby.