It is an ecologically flexible species, able to adapt to various resource and space conditions, and its diet follows this pattern; it is considered opportunistic and omnivorous.

It can also be used as a living indicator for environmental conditions, as the composition of its scales often reflects the availability of different resources in its environment, and it responds to various pollutants in ways that can be easily measured.

Some researchers consider it synonymous with Astyanax lacustris, but there are various data that suggest the two should remain separate, including chromosomal, mitochondrial, and geographical.

Genetic evidence supports a possible second species within A. altiparanae's current definition; there are at least two distinct haplotypes, or sets of alleles clearly inherited from one lineage over another.

[9] Its maximum weight is 60 g.[citation needed] Its base body color is generally a dark silver, with bright-yellow fins, and the darker dorsal region fades into a whitish ventral region;[2] when exposed to the stressful conditions of lowered water temperature, these colors darken to a dark-gray and more desaturated yellow.

[15][16] It was momentarily thought to be endemic to the upper Paraná basin, but this has since been disproved;[17] A. altiparanae is an incredibly widespread species, thanks largely to its adaptability.

[18] Astyanax altiparanae tends to occupy the upper portion of the water column, but this preference is only demonstrated in areas with ample space for groups to spread out.

Smaller individuals form larger schools of approximately 50 fish, and stay near the surface of the water; they more often occupy space near the riverbanks (especially when there is plentiful aquatic vegetation).

)[12] The rainy season correlates with higher consumption of allochthonous material, especially at sites with ample riparian vegetation and especially in terms of arthropods.

This may be due to oregano oil's antimicrobial properties, which could have reduced the relevant negative activity in the intestines; without the resource expenditure of replacing damaged cells therein, overall growth may have been improved.

)[17] Specific predators of A. altiparanae include Salminus hilarii and Hoplias malabaricus, which rely heavily upon it in the Corrente River,[27] as well as characid species Acestrorhynchus lacustris.

[23] This is especially the case given the fact that it can change its diet to fit its surroundings, and its physiological response therefore reflects the health and primary food sources it utilizes within said environment.

[34] Upon early research (yet unreviewed), various types of textile dyes were also discovered to have apparent genotoxic effects upon A. altiparanae, which broadens the range of contaminants it can signal.

[36] Astyanax altiparanae has been recently, and strongly, considered for status as a model organism - that is, a species upon which various tests can be performed in laboratory conditions, yielding data and techniques that go on to be useful in related research.

[3] It is also readily available from the commercial market, which makes it easy to obtain and therefore experiment with, as long as natural environmental conditions are not being taken into consideration.

[43] Similarities in mitochondrial DNA between two separate populations of A. altiparanae helped to broaden its range in the early years of its discovery and study.

[45] Higher reproduction rates in the rainy season can possibly be explained by an increase in food availability; specifically, A. altiparanae would be feeding upon allochthonous material washed in from the surrounding environment.

[46] Astyanax altiparanae has been considered for surrogate propagation, a process that allows animals to produce gametes from another species, which would be used in the conservation of endangered relatives.

[49] Another method, considered more reliable for continued production, is to breed tetraploid females and haploid males, which results in triploid offspring.

[51] It is already a large part of aquaculture in South America because it can be used for various purposes, such as food or live bait, and a high production of captive specimens reduces the risk of overfishing.

[citation needed] A hormonal treatment called Carp Pituitary Extract (CPE) has been proven as a way to increase reproduction rates in captive female specimens.

[53] A. altiparanae also tolerates limited salinity, which can be used to mitigate stress responses as well; in some fish species, blood glucose rises upon agitation, possibly to prepare the animal for a fight-or-flight scenario.

[1] This is positive for various aspects of the regions it inhabits, partially due to its important role in a low tier on the food chain, serving as a source for various piscivores.

[24] Efforts to ensure A. altiparanae's continued success should take the health of riparian vegetation into consideration, as allochthonous material makes up a great deal of its diet in regions without adequate waterborne resources.