Taxonomy & naming
Akysis portellus was described by Heok Hee Ng in 2009, one of many small stream-dwelling Akysis species named from Southeast Asia in the 2000s as the genus was surveyed more thoroughly. It belongs to the family Akysidae, the stream catfishes of Asia, a family of small, flattened, hillstream-adapted catfishes distinct from the unrelated Sisoridae with which they are sometimes confused in older literature.
The genus Akysis is large, with dozens of narrow-range species scattered across South and Southeast Asian drainages, many of them — like A. portellus — known only from their type stream or a small cluster of nearby localities. The Catalog of Fishes treats Akysis portellus as the valid combination; there is no older synonymy to correct here, as the species has always sat in Akysis since its description.
Morphology
This is one of the smallest catfishes an aquarist will ever encounter: the maximum recorded size is 1.5 in standard length (some FishBase citations report figures closer to 1.5 in SL, likely reflecting different sampled populations or measurement conventions, but both confirm a genuine dwarf). Like other akysids it has a flattened head, a slender body tapering to the tail, and barbels around the mouth for feeling out prey and substrate in the dark or in turbid hillstream water.
The skin is naked — akysids, like nearly all catfishes, have no scales — which makes the species considerably more sensitive to copper-based medications and some other treatments than scaled fish; a conservative, often half-strength dose is the safer approach if treatment is ever needed. As in other Akysis, the dorsal and pectoral fins carry stiff, serrated spines that lock erect and house a venom apparatus at their base, capable of delivering a genuinely painful sting; the spines also snag readily in aquarium nets, so the fish is best scooped and moved in a small container rather than netted.
Habitat
Akysis portellus is known only from the Shwe Kyin stream, a tributary of the Sittaung River in Bago Region, southern Myanmar — a narrow-range endemic with, as far as is documented, no confirmed populations outside this single drainage. Streams of this kind are typically clear, flowing hillstream habitats with rocky or gravel substrates and moderate current, though fine-scale habitat descriptions for this particular species are sparse.
Water conditions reported for the species are cool to moderate and soft to neutral: temperatures of roughly 62–75 °F, pH 6.0–7.5, and hardness in the 36–215 ppm range. That temperature band is notably cooler than the tropical 75–82 °F most aquarium catfish are kept at, reflecting a hillstream rather than lowland tropical origin, and it should be respected rather than assumed away.
Feeding
Data specific to A. portellus's wild diet is sparse, but the genus Akysis is characteristically a nocturnal benthic micropredator, foraging over the stream bottom after dark for small aquatic crustaceans, worms, insect larvae and zooplankton rather than grazing algae or detritus in the manner of some other small catfishes.
In the aquarium this species does best on small live or frozen foods — Artemia (brine shrimp), Daphnia and bloodworm are all reported as readily accepted — and it often refuses dried foods outright, so keepers should not rely on flake or pellet alone. Offering food after lights-out, when the fish is naturally active, gives it a better chance of getting fed in a mixed setup without being out-competed by faster diurnal tankmates.
Mating
No courtship or spawning behaviour has been documented for Akysis portellus itself; the species' breeding biology in the wild is effectively unrecorded. The closest documented data point among its relatives comes from A. vespa, a similar small Akysis that was induced to spawn in captivity following a deliberate drop in temperature of around 45 °F, suggesting a seasonal or rain-triggered spawning cue is plausible for the genus generally — but this is inference from a relative, not confirmed observation of A. portellus.
Breeding
Breeding of Akysis portellus has not been reported in the aquarium hobby or in the scientific literature, and nothing is known of its egg deposition site, fecundity, or parental care. Given the temperature-drop spawning trigger recorded in the related A. vespa, a seasonal cooling cue is a reasonable working hypothesis for hobbyists wanting to attempt breeding this species, but it should be treated as speculative rather than an established protocol. As with most small, narrow-range Akysis, this is not a fish with an established home-breeding pathway — the aquarium supply, where it exists at all, is assumed to be wild-collected.
In the aquarium
Because the confirmed adult size is only around 1.5 in SL, Akysis portellus never needs — and should never be kept in — anything but a genuinely small setup; this is one of the very few catfish where the size trap runs in the opposite direction, and a nano hillstream-style aquarium suits it far better than a large community tank. Keep water cool relative to typical tropical community norms (roughly 62–75 °F), soft to neutral (pH 6.0–7.5), with good flow and oxygenation to mimic its native stream, and provide fine gravel or sand plus cover such as smooth rocks or driftwood for a fish that is most active after dark.
Its scaleless skin means conservative dosing of copper-based medications and many other treatments, in line with loaches, puffers and other naked-skinned catfishes. Its dorsal and pectoral spines lock and carry venom, so it should be moved in a cup or container rather than chased with a net, both to protect the fish's fins and to avoid a painful jab to the keeper. Given its tiny size, keep it only with other diminutive, peaceful, cool-to-moderate-water species — nothing large enough to see it as food.
Conservation
The IUCN Red List assesses Akysis portellus as Data Deficient, reflecting how recently it was described (2009) and how little targeted survey work has been done on its single known stream. As a narrow-range endemic restricted to the Shwe Kyin stream in the Sittaung drainage, it is inherently vulnerable to any localised habitat pressure — deforestation, agricultural runoff, damming or water extraction — even though no formal threat assessment yet quantifies that risk. Its conservation status should be treated as genuinely unknown rather than as evidence of safety.