''Symphysodon tarzoo'', the green discus, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of cichlid native to rivers of the western Amazon Basin upriver from the Purus arch, although it occasionally occurs downstream. An introduced population in the

Nanay River The Nanay River is a river in northern Peru. It is a tributary of the Amazon River, merging into this river at the city of Iquitos. The lower part of the Nanay flows to the north and west of the city, while the Itaya River flows to the south an ...

is based on stock from the Tefé region. The green discus is found in blackwater habitats with a high temperature of and low pH of 4.8–5.9. Although also known from

whitewater Whitewater forms in a rapid context, in particular, when a river's gradient changes enough to generate so much turbulence that air is trapped within the water. This forms an unstable current that froths, making the water appear opaque and ...

, its preference for

lentic A lake ecosystem or lacustrine ecosystem includes biotic (living) plants, animals and micro-organisms, as well as abiotic (non-living) physical and chemical interactions. Lake ecosystems are a prime example of lentic ecosystems (''lentic'' re ...

habitats such as

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

s means that the water contain little suspended material (unlike main sections of whitewater rivers). This species grows to a length of SL. ''S. tarzoo'' has red spots on the anal fin and body, which separates it from other discus species. The scientific name was coined by Earl Lyons in 1959, and the species was revalidated by pattern,

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

and

mtDNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DNA ...

in 2006. Later studies have confirmed its distinction, although some suggest the correct scientific name for the green discus is ''S. aequifasciatus'' (a name typically used for the blue/brown discus). No natural (wild) hybrids are known between the green discus and its relatives.

References

tarzoo Fish described in 1959 {{Cichlidae-stub