Taxonomy & naming
Phycocharax rasbora was described by Ohara, Mirande & Lima in 2017, making it one of the most recently erected species in the genus. The valid name as recognised by Eschmeyer's Catalog of Fishes (Catalog of Fishes, CAS) is Phycocharax rasbora Ohara, Mirande & Lima, 2017. The genus Phycocharax belongs to the vast family Characidae — the largest family of freshwater fishes — within the order Characiformes. Detailed phylogenetic placement and close relatives within Characidae await further systematic work, as the genus is small and the 2017 description is recent.
The specific epithet rasbora alludes to the species' superficial resemblance to Old World rasboras (family Cyprinidae), a striking case of convergent body form across distantly related freshwater fish lineages. The genus name Phycocharax combines the Greek phykos (seaweed or algae) with charax, a general Characiform root, possibly in reference to habitat associations or coloration, though the exact intended derivation is detailed in the original description.
Morphology
Phycocharax rasbora is a very small tetra, with FishBase recording a maximum standard length of 1.5 in. At this size it falls among the miniature characids, comparable in scale to many of the small tetras of the genera Hemigrammus and Hyphessobrycon. The body form is elongate and laterally compressed, lending the fish the rasbora-like silhouette that inspired its species epithet.
Detailed morphological data — fin-ray counts, lateral-line scale counts, and specific colour-pattern characters — are documented in the original 2017 description but are not reproduced here in the absence of the primary literature. As with many small tetras, the genus likely shows modest sexual dimorphism in body depth and fin shape, though specific notes on dimorphism in this species are sparse in the available secondary literature.
Habitat
Phycocharax rasbora is a South American freshwater species within the family Characidae, and like most of its relatives it likely inhabits smaller streams, tributaries, or flooded zones in the South American interior. Precise type-locality data and habitat descriptions are contained in the original 2017 description by Ohara, Mirande & Lima, which has not been widely reproduced in the secondary literature consulted here.
Water-chemistry parameters — temperature, pH, conductivity — specific to its natural range are not documented in available sources. Given its taxonomic position among small South American characids, it likely tolerates the soft, warm, slightly acidic to neutral freshwater conditions typical of lowland stream habitats, but these values should not be assumed without primary data.
Feeding
No specific dietary studies have been published for Phycocharax rasbora. Small characids of comparable size are broadly omnivorous, feeding opportunistically on microinvertebrates, small aquatic insects, zooplankton, and organic detritus in the water column and at the surface. Based on body size and guild placement, Phycocharax rasbora almost certainly feeds in a similar manner in the wild.
In the aquarium — where the species is not established in the hobby at the time of writing — small live and frozen foods such as Artemia nauplii, micro-worms, and finely crushed flake would be expected to be accepted by fish of this size class. Data on captive feeding behaviour are sparse.
Mating
No detailed observations of mating behaviour have been published for Phycocharax rasbora. Small tetras in Characidae broadly are egg-scattering open spawners: males court females without constructing nests, and pairs or groups scatter adhesive or semi-adhesive eggs among fine-leaved plants or over substrate, with no subsequent parental care.
In the absence of species-specific data, a similar egg-scattering strategy can be reasonably inferred for Phycocharax rasbora, consistent with the reproductive mode of the broader family. Any detailed observations of courtship display, spawning substrate preferences, or spawning season would require fieldwork at the type locality or dedicated captive-breeding studies that have not been reported in the accessible literature.
Breeding
Breeding in captivity has not been documented in the available literature for Phycocharax rasbora, and the species does not appear to be established in the ornamental-fish trade as of its description in 2017. By analogy with other miniature South American tetras, breeding would likely follow the typical characid pattern: adhesive eggs scattered among fine-leaved plants, hatching within one to three days at warm temperatures, with adults offering no parental care and liable to consume eggs if not removed.
Fry of small tetras require very fine first foods — infusoria or commercial micro-fry preparations — before graduating to newly hatched brine shrimp. These inferences are extrapolated from the broader family; species-specific breeding data for Phycocharax rasbora remain to be established.
In the aquarium
Phycocharax rasbora is not a species currently found in mainstream ornamental-fish keeping. It was described from scientific collections in 2017, and no hobbyist accounts or care guides appear in the available literature. As a small characid of under 1.5 in, it would be suited in principle to nano or planted aquaria, kept in a group with similarly sized, peaceful tankmates.
Should it become available in the trade, husbandry parameters drawn from comparable miniature South American tetras would provide a useful starting point: warm, soft to moderately hard, slightly acidic to neutral water; a densely planted or well-structured tank with gentle flow; small live and frozen foods as a dietary staple. Its small size and probable peaceful disposition would make it an attractive subject for specialist keepers, but current data on captive requirements are absent.
Conservation
Phycocharax rasbora has not been assessed by the IUCN Red List as of the time of this writing. The species was described in 2017, and recently described fishes frequently remain unevaluated for some years after their formal description. In the absence of an IUCN assessment, its conservation status is unknown (Not Evaluated).
Given the ongoing pressures facing freshwater biodiversity in South America — habitat loss, deforestation of riparian zones, water extraction, and pollution — small, range-restricted species described from limited localities can be particularly vulnerable. Understanding the actual range, population size, and habitat specificity of Phycocharax rasbora would be a prerequisite for any meaningful conservation evaluation.