Symphysodon tarzoo

Symphysodon tarzoo, the green discus, is a species of cichlid native to rivers of the western Amazon Basin upriver from the Purus arch, although it occasionally occurs downstream.[1][2] An introduced population in the Nanay River is based on stock from the Tefé region.[3] The green discus is found in blackwater habitats with a high temperature of 27–30 °C (81–86 °F) and low pH of 4.8–5.9.[3] Although also known from whitewater, its preference for lentic habitats such as floodplains means that the water contain little suspended material (unlike main sections of whitewater rivers).[2][4]

Green discus
Individuals from Nanay (above) and Japurá Rivers (below)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Cichliformes
Family:	Cichlidae
Genus:	Symphysodon
Species:	S. tarzoo
Binomial name
Symphysodon tarzoo Lyons, 1959

This species grows to a length of 13.2 centimetres (5.2 in) SL.[1][5] S. tarzoo has red spots on the anal fin and body, which separates it from other discus species.[6]

The scientific name was coined by Earl Lyons in 1959, and the species was revalidated by pattern, morphology and mtDNA in 2006.[1][6] 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).[2][3] No natural (wild) hybrids are known between the green discus and its relatives.[1][3]