Taxonomy & naming
Steindachnerina varii was described by Jacques Géry, Régine Planquette and Pierre Le Bail in 1991. The species name commemorates the American ichthyologist Richard P. Vari, whose taxonomic revision of Steindachnerina and the broader Curimatidae in the 1980s and 1990s untangled a genus that had accumulated a long history of confused and overlapping names. In a taxonomic note tied to the original description, Vari (1993) himself established S. varii as the correct name for this fish over an alternative name, S. runa, that had also circulated for populations in the same coastal drainages — a small but real example of the nomenclatural housekeeping typical of this family.
The genus Steindachnerina sits within Curimatidae, in the order Characiformes, and takes its own name from the Austrian ichthyologist Franz Steindachner. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the governing authority for the valid combination Steindachnerina varii, and no revision affecting this species' placement has been noted here; this account keeps the name as described. Steindachnerina varii is one of many small, similar-looking curimatid species scattered across South American coastal and lowland rivers, and field identification within the genus generally requires close comparison of scale counts, mouth position and body proportions rather than colour pattern alone.
Morphology
Steindachnerina varii is a small, laterally compressed characin reaching a maximum recorded standard length of about 3.5 in, placing it firmly among the modest-sized grazers of Curimatidae rather than anywhere near the large-bodied piranhas, pacus or dorados that share this atlas grouping. Like other curimatids, it has a small, subterminal or slightly underslung mouth adapted for scraping algae and organic material from surfaces rather than for grasping prey, and it lacks the well-developed, blade-like dentition that defines true piranhas in the family Serrasalmidae.
Detailed published description of colour pattern and fin proportions for this species is sparse in the sources available here; curimatids as a group are typically silvery-plain fish with little ornamentation, and Steindachnerina varii is not documented as an exception. Data on this point is sparse and should not be embellished.
Habitat
Steindachnerina varii is known from coastal river drainages of northeastern South America between the Suriname and Oyapock rivers — a stretch of Atlantic-draining freshwater systems spanning the coast of Suriname and French Guiana (and, by extension, adjacent Guyana). It has been confirmed in Suriname's coastal drainages and in the Oyapock river system that forms part of the French Guiana–Brazil border.
FishBase records the species as a benthopelagic freshwater fish of a subtropical/tropical climate. Specific water chemistry data (pH, hardness, exact temperature range) for the type locality is not given in the sources consulted for this account; readers should treat any numeric range beyond "warm, tropical South American coastal river conditions" as unconfirmed rather than guess at figures.
Feeding
Steindachnerina varii feeds on algae, consistent with the typical benthic-grazing habit of Curimatidae: a small, downturned mouth used to rasp algal film and associated organic material from submerged surfaces and substrate rather than to take other fish or large invertebrate prey. FishBase notes the species appears to live in groups, which fits the shoaling, substrate-grazing lifestyle typical of small curimatids moving together over river-bottom feeding grounds.
No aquarium feeding data exists for this species specifically. Based on its documented wild diet and its family's general habits, a keeper would be expected to offer a herbivore-leaning diet of algae wafers, blanched vegetables and fine flake or micro-pellet foods, but this is an inference from its biology rather than a reported aquarium practice.
Mating
No courtship or spawning behaviour has been documented for Steindachnerina varii in the sources consulted here. The species has not been kept or bred in the aquarium hobby to any documented extent, so there is no hobbyist account of pairing, colour change or courtship display to draw on, and none should be invented.
Breeding
There are no aquarium-breeding records for Steindachnerina varii. As a small curimatid characin, it most plausibly follows the open-water egg-scattering pattern common to many minor grazing characins in this broader "Hemiodus & minor characins" group — a shoal spawning event with no parental care — but this is a family-level inference, not a confirmed observation for this species, and it should be read as such rather than as documented fact.
In short: breeding mode, fecundity, egg characteristics and development time are all unknown for Steindachnerina varii. This is an honest gap in the record rather than an oversight in this account.
In the aquarium
Steindachnerina varii is not an established aquarium fish. It does not appear to be part of the ornamental trade, and none of the sources consulted document tank requirements, compatible tankmates or long-term husbandry for the species. Given its small adult size (under 4 in) and grazing, group-living habits documented in the wild, a keeper attempting the species would reasonably plan for a modest shoal in a planted or driftwood-furnished setup with stable, warm tropical water and a grazing-friendly diet — but this is a reasonable extrapolation from its biology, not a tested care regime.
Prospective keepers should treat this species as effectively unavailable and undocumented in captivity, and should not expect to find husbandry guides, breeding reports or even confirmed photographs from aquarium sources.
Conservation
Steindachnerina varii has not been evaluated by the IUCN Red List (status: Not Evaluated). This is unsurprising for a small, range-restricted coastal curimatid with a narrow geographic footprint between the Suriname and Oyapock rivers and little economic or ornamental profile to attract dedicated assessment.
No specific threats to the species have been documented in the sources consulted here. Its native coastal Guianas range sits within a region facing general pressures common to northeastern South American freshwater systems — land-use change, mining-related sedimentation and water-quality impacts in some catchments — but no source consulted ties a specific threat or population trend to Steindachnerina varii itself, so none is asserted.