Due to their distinctive shape, calm behavior, many bright colors and patterns, and dedicated parenting techniques, discus are popular as freshwater aquarium fish, and their aquaculture in several countries in Asia (notably Thailand)[1] is a major industry.

[6][7] The discus fish has attracted a cult following of collectors and has created a multimillion dollar international industry complete with shows, competitions, and reputable online breeders[citation needed].

Whether S. haraldi is indeed distinct from S. aequifasciatus remains to be determined; if valid it is widespread but it might just be a color morph.

[citation needed] A molecular study in 2011 found five main groups, which generally matched previously recognized phenotypes.

[14] Their assigning of scientific names to species differed to some extent from that used by earlier authors: Heckel (S. discus; Rio Negro, upper Uatumã, Nhamundá, Trombetas and Abacaxis), green (S. tarzoo; West Amazon drainages upriver from the Purus Arch, blue (S. sp.

[14] This taxonomy with four described valid species, S. discus, S. tarzoo, S. haraldi and S. aequifasciatus, has been adopted by the Catalog of Fishes.

[16] Like cichlids from the genus Pterophyllum (angelfish), all Symphysodon species have a laterally compressed body shape.

[18] Discus fish exhibit no sexual dimorphism when they are under about 4 inches in size, making it difficult to distinguish between males and females at a young age.

The only definitive way to confirm the sex of discus fish is by observing spawning behavior, where a female lays eggs and a male swims over to fertilize them.

are highly social, typically occurring in groups that may number many dozens of individuals, which is unique among cichlids of the Americas.

This parent-to-offspring transmission of important microorganisms might explain the high survival rate of discus fry raised with their parents, compared to the low survival rate of progeny raised artificially by fish breeders (e.g. on egg yolk, brine shrimp, or other replacement foods).

primarily feed on algae, other plant material, and detritus (periphyton), but also eat small invertebrates.

[19] Symphysodon species inhabit the margins of floodplain lakes and rivers in the lowland Amazon basin,[19] where they are part of the highly diverse Neotropical fish fauna.

[8] In contrast, the distribution of S. discus appears to be limited to the lower reaches of the Rio Negro, upper Uatumã, Nhamundá, Trombetas, and Abacaxis Rivers.