''Symphysodon aequifasciatus'', the blue discus or brown 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 ...

cichlid Cichlids are fish from the family Cichlidae in the order Cichliformes. Cichlids were traditionally classed in a suborder, the Labroidei, along with the wrasses ( Labridae), in the order Perciformes, but molecular studies have contradicted this ...

native to rivers of the eastern and central

Amazon Basin The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Bolivi ...

downriver from the

Púrus Arch The Púrus Arch ( pt, Arco do Purus) is a basement high in Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 mil ...

. This discus is found in black-, clear- and

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 ...

, but its preference for

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

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 and

flooded forest Freshwater swamp forests, or flooded forests, are forests which are inundated with freshwater, either permanently or seasonally. They normally occur along the lower reaches of rivers and around freshwater lakes. Freshwater swamp forests are found ...

s means that the whitewater it inhabits contain little suspended material (unlike main sections of whitewater rivers). It is largely restricted to water with a high temperature of and a pH of 5.2–7.7. It typically reaches a length of up to SL, but captives have been claimed to reach . It is commonly kept in

aquarium An aquarium (plural: ''aquariums'' or ''aquaria'') is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aq ...

Taxonomy

The

taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

is disputed, but

FishBase FishBase is a global species database of fish species (specifically finfish). It is the largest and most extensively accessed online database on adult finfish on the web.

follows a review of the genus from 2006. In 2007 it was suggested that the correct scientific name of the blue/brown discus is ''S. haraldi'', whereas ''S. aequifasciatus'' is the correct name for the

green discus ''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. An introduced population in the Nanay River is based on sto ...

. In 2011 a study indicated that it should be split into three: Brown discus (''S. aequifasciatus''; East Amazon downriver from

Meeting of Waters The Meeting of Waters ( pt, Encontro das Águas) is the confluence between the dark (Blackwater river, blackwater) Rio Negro (Amazon), Rio Negro and the pale sandy-colored (Whitewater river (river type), whitewater) Amazon River, referred to as ...

), blue discus (''S.'' sp. 1; central Amazon from Purus arch to the Meeting of Waters) and the Xingu group (''S.'' sp. 2; Xingu and

Tocantins Tocantins () is one of the 26 states of Brazil. It is the newest state, formed in 1988 and encompassing what had formerly been the northern two-fifths of the state of Goiás. Tocantins covers and had an estimated population of 1,496,880 in 20 ...

). The Xingu group currently lacks a scientific name, but it is possible that the correct name for the blue is ''S. haraldi''. This taxonomy where both ''S. haraldi'' and ''S. aequifasciatus'' are recognized as described valid species has been adopted by the

Catalog of Fishes Catalog of Fishes is a comprehensive on-line database and reference work on the scientific names of fish species and genera. It is global in its scope and is hosted by the California Academy of Sciences. It has been compiled and is continuously up ...

. Some

hybridization Hybridization (or hybridisation) may refer to: *Hybridization (biology), the process of combining different varieties of organisms to create a hybrid *Orbital hybridization, in chemistry, the mixing of atomic orbitals into new hybrid orbitals *Nu ...

occurs (or has occurred) between the species recognized in the 2011 study and also between the brown and

Heckel discus ''Symphysodon discus'', the red discus or Heckel discus, is a species of cichlid native to the Amazon Basin, where found in the lower Rio Negro, upper Uatumã, Nhamundá, Trombetas The Trombetas is a large river on the northern side of the ...

(''S. discus''), but overall they maintain their separate evolutionary trajectories.

References

{{Taxonbar, from=Q3091839 Cichlid fish of South America Fish described in 1904 Taxa named by Jacques Pellegrin aequifasciatus