Most Astyanax spp. are not popular in the aquarium hobby, though the genus is among the most speciose within the family Characidae. A. leopoldi is no exception in that you’ll rarely see it offered for sale but may find the occasional specimen mixed among other species in shipments of wild fishes from Peru.

While the surface-dwelling form of this species is fairly unremarkable and rarely-seen in the hobby, the blind form is very popular indeed. The two may have diverged as recently as within the last 10,000 years, with the blind form losing its eyes and much of its pigment. This probably happened because the fish needed better development in other sensory areas. Losing unnecessary and energy-consuming aspects of its physiology allowed it to devote more energy to developments such as increased numbers of taste receptors on the head.

A. bimaculatus is not a popular aquarium fish but is available on occasion exception, most often as a contaminant among shipments of other species.

It’s identity is also in question to an extent with the name currently applied to what is considered to represent a species complex comprising at least four taxa.

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.

A good beginner’s tetra, as it’s a hardy species that will adapt to a relatively wide range of conditions. In a well-insulated house it can even be kept in an unheated tank, although it won’t be as colourful as when kept in warmer water.

It’s also quite long-lived and captive specimens over ten years old are not unheard of…

Choice of décor is not especially critical although it tends to show better colouration when maintained in a well-furnished set-up with live plants and a dark substrate.

A natural-looking arrangement might consist of a soft, sandy substrate with wood roots and bran…

In the aquarium hobby the name Hyphessobrycon stegemanni has frequently been misapplied to a species that has been described as Hemigrammus ataktos Marinho, Dagosta, & Birindelli 2014. The reasons for this confusion are presumably that the two occur sympatrically in the rio Tocantins system and both possess a dark lateral stripe on the body.

The most recent diagnosis appears to be that of Géry (1977), in which it was separated from other members of the group by the following combination of characters: dorsal-fin insertion at or slightly anterior to mid-body; caudal-fin brick red to orange-red; body depth fits less than 3.6 times in SL; head length fits 3.5-4.0 times in SL; caudal peduncle length u…

This species is occasionally available in the aquarium trade, although usually as bycatch among shipments of other fishes.

It is sometimes traded as H. sp. ‘Araguaia red’, H. sp. ‘Araguaia’ or ‘Schultz’s tetra’.