Taxonomy & naming
Schistura rikiki was described by the Swiss ichthyologist Maurice Kottelat in 2000, placed from the outset in the genus Schistura within the family Nemacheilidae — the stone and brook loaches, the largest family within the loach superfamily Cobitoidea. Nemacheilidae has been extensively reshuffled over the past few decades as older catch-all genera such as Nemacheilus and Noemacheilus were split apart; Schistura is one of the genera that absorbed much of that diversity, and the Catalog of Fishes (Eschmeyer, CAS), the authority for valid names, continues to list this species under its original combination.
The specific epithet rikiki is not Latin or Greek but French colloquial slang for something diminutive or pint-sized, a fitting name for one of the smaller fish in an already small-bodied genus. No English or trade common name is established for this species; it is essentially unknown in the aquarium hobby and is referred to by its scientific name.
Morphology
Schistura rikiki is a minute stone loach, reported to reach only about 1 in in standard length — small even by the standards of Nemacheilidae, a family already made up mostly of slender, elongate, bottom-hugging fish. As in other members of the genus it almost certainly carries the erectile suborbital spine typical of loaches in this superfamily, a defensive spine folded into a groove beneath the eye, along with the small, deeply embedded scales or near-scaleless skin characteristic of the group — a feature that matters for how sensitive these fish are to medication.
Detailed morphological description beyond the type material is sparse in the sources available here; like many narrow-range Laotian Schistura, this species is known mainly from its original description and has not been the subject of further published study.
Habitat
The species is known only from the Se Kong (Xe Kong) river basin of southern Laos, with its type locality on the Xe Kong between Attapu and Ban Ouk. It is associated with the Xe Kong and Xe Kaman river systems and inhabits riffles — the shallow, fast-flowing, well-oxygenated stretches of stream — over gravel and stone substrates, the classic habitat for small benthic Schistura throughout mainland Southeast Asia.
Water conditions have not been directly measured for this species in the sources here, but related Schistura from similarly structured Laotian streams are recorded in clear, well-oxygenated water in the mid-20s °C, over coarse sand, gravel, rocks and boulders. As a small riffle-dweller from a mountain-fed tributary system, Schistura rikiki most likely favours cool-to-moderate, fast-flowing, highly oxygenated water rather than warm, still conditions — but this should be read as an inference from its habitat and relatives rather than a directly documented figure.
Feeding
No dietary data specific to Schistura rikiki was found in the sources consulted. Stone and brook loaches as a group are bold benthic micro-predators, working riffle substrates for small invertebrates and insect larvae rather than grazing algae or taking food from the water column, and there is no reason to expect this tiny riffle-dwelling species to differ from that general pattern.
In the near-total absence of aquarium accounts for this species, any feeding regime would have to be inferred from its close relatives and its habitat rather than from direct observation — small live or frozen foods sized to a 1 in fish, offered on or near the substrate, would fit the general micro-predator profile of the genus.
Mating
Nothing specific to the courtship or spawning behaviour of Schistura rikiki was found in the sources consulted. Stone and brook loaches in general show no obvious external sexual dimorphism beyond females running heavier with eggs when in condition, and reproduction in the wild is generally tied to seasonal high-flow periods over gravel riffles rather than to any elaborate pairing behaviour. Data for this specific, narrow-range species simply does not exist in the record available here.
Breeding
There are no records of Schistura rikiki being bred in captivity, and no aquarium-trade presence to draw on. As with the great majority of Nemacheilidae, the expected pattern — inferred from the family rather than documented for this species — is an egg-scatterer that releases eggs over gravel in fast-flowing water with no parental care, a strategy shared across the stone and brook loaches. This is a fish that is, for all practical purposes, never seen or bred in the hobby; the honest statement is that its reproductive biology remains undocumented.
In the aquarium
Schistura rikiki has essentially no presence in the aquarium trade — it is a narrow-range stream endemic known from a single Laotian river basin, not a fish that is collected or exported for the hobby. Should material ever become available, the general rules for small riffle-dwelling Nemacheilidae would apply: a well-oxygenated tank with strong flow, a substrate of gravel and smooth stone, and cool-to-moderate rather than warm, still water, since this is a species from fast mountain-fed tributaries, not stagnant lowland habitat.
As with other members of the superfamily Cobitoidea, its near-scaleless skin would be expected to make it highly sensitive to copper-based medications and full-strength treatments generally, warranting the same caution used with other scaleless loaches. Given the total lack of documented husbandry, none of this can be stated as established aquarium practice — it is a reasonable extrapolation from the family, not a record of anyone having kept the species.
Conservation
Schistura rikiki is assessed by the IUCN Red List as Data Deficient, reflecting the general pattern for narrow-range Laotian Nemacheilidae: insufficient information exists to evaluate its extinction risk. Known only from the Se Kong basin, it shares the vulnerability common to single-river-system endemics — any pressure on that watershed, whether from damming, sedimentation or water extraction, has an outsized effect on a species with nowhere else to go.
There is no evidence in the sources consulted of an aquarium trade in this species, so collecting pressure is not a documented concern; the open question is simply how much of its actual population and range remain unassessed. As with much of the Mekong basin's tributary ichthyofauna, better survey data would be needed before its status could be refined beyond Data Deficient.