C. aurofrenatus is currently understood to occur throughout much of the Río Paraguay-Paraná system in Paraguay, and has also been recorded in Argentina and Bolivia.

It was described from Paraguay with type locality given as ‘Aguada near Arroyo Trementina’. The latter is stated to be a tributary of the ‘Rio Aquido Canigi’.

Widely-distributed throughout much of the Paraná and Uruguay river systems in Brazil, Paraguay, Argentina and Uruguay.

Some records from Buenos Aires province, Argentina are now considered to refer to the congener H. togoi (Miquelarena and López, 2006) so the common vernacular name ‘Buenos Aires tetra’ may not…

It exhibits slightly different behaviour to the majority of congeners in that it tends to swim in midwater and spends a large proportion of its time away from the substrate. Its morphology exhibits corresponding adaptations towards a pelagic existence with a relatively large eye, a more terminal mouth position, more strongly-forked caudal-fin, and more symmetrical body shape than most other Corydoras species.