T. stellatus is superficially similar to its only congener T. securis, but can immediately be identified by the presence (vs. absence) of a prominent dark spot in the dorsal-fin. It is sometimes traded as ‘platinum hatchetfish’.

The genus Thoracocharax was originally erected by Fowler in 1906 as a subgenus of Gasteropelecus, but was elevated to generic status by Weitzman (1960).

This species is normally referred to as A. paraguayensis, but that name has been considered a synonym of A. nattereri since 2003.

Confusion remains however, as the type locality for the latter is ‘Villa Bella’, now known as Parintins, a settlement on the main Amazon river channel between Manaus and Santarém and many kilometres away from the majority of confirmed localities.

Endemic to the Paraguay, Paraná and Uruguay river drainages in Brazil, Paraguay, Argentina and Uruguay.

The smallest of the three Aphyocharax species seen in the hobby, the redflank is relatively uncommon in the hobby in the aquarium trade.

It is also known as the Green Fire Tetra.

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.