Discus (fish)

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Symphysodon
Blue Discus.jpg
Symphysodon aequifasciatus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cichliformes
Family: Cichlidae
Tribe: Heroini
Genus: Symphysodon
Heckel, 1840
Type species
Symphysodon discus
Heckel, 1840
Species

See text

Symphysodon (colloquially known as discus or discus fish) is a genus of cichlids native to the Amazon river basin in Brazil. 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. [2] [3] [4] [5] They are sometimes referred to as pompadour fish. [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 ].

Contents

Species

Following a review published in 2006, [8] three species are recognized by FishBase: [9]

ImageNameDistribution
Nikolaevskii zoopark. Akvarium.8 - panoramio.jpg Symphysodon aequifasciatus Pellegrin, 1904 (blue discus or brown discus)central Amazon Basin
Symphysodon discus 02.jpg Symphysodon discus Heckel, 1840 (red discus or Heckel discus)Amazon Basin
Green Japura.JPG Symphysodon tarzoo E. Lyons, 1959 (green discus)western Amazon Basin

Taxonomy

Symphysodon discus Discus heckel.jpg
Symphysodon discus

Discus are fish from the genus Symphysodon, which currently includes the species S. aequifasciatus, S. discus and S. tarzoo, based on a taxonomic review published in 2006. [8] [10] A review published in 2007 largely came to the same result, but differed in nomenclature, as the species called S. tarzoo in the 2006 study was called S. aequifasciatus in the 2007 study, and S. aequifasciatus in 2006 was S. haraldi in 2007. [11] [12] Further arguments have been made that S. tarzoo was not described in accordance with ICZN rules and thus should be considered invalid and replaced with S. haraldi, [13] currently considered a synonym of S. aequifasciatus by FishBase.

Other species and subspecies have been proposed, but morphometric data (unlike in Pterophyllum , the freshwater angelfish) varies as much between individuals from one location as across the whole range of all discus fish species.[ citation needed ]S. tarzoo was described in 1959 and applies to the red-spotted western population. S. aequifasciatus and S. discus, meanwhile, seem to hybridise frequently in the wild or have diverged recently, as they lack mitochondrial DNA lineage sorting but differ in color pattern and have dissimilar chromosomal translocation patterns. S. discus occurs mainly in the Rio Negro. 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 ]

Two captive variants (orange and solid turquoise) Symphysodon aequifasciatus (1) 03May2010.JPG
Two captive variants (orange and solid turquoise)

A molecular study in 2011 found five main groups, which generally matched previously recognized phenotypes. They recognized them as evolutionarily significant units and species. [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. 1; central Amazon from Purus Arch to the Meeting of Waters), brown (S. aequifasciatus; East Amazon downriver from Meeting of Waters), Xingu group (S. sp. 2; Xingu and Tocantins). [14] The Xingu group currently lacks a scientific name, but it is possible that the correct name for the blue is S. haraldi. [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. [15] Some hybridisation occurs (or has occurred) between the brown discus and neighbouring forms, but overall they maintain their separate evolutionary trajectories. [14]

In addition to the wild discus, several captive variants achieved by selective breeding exist. Based on RAPD sequences, the captive variants popularly known as turquoise, pigeon, ghost, cobalt and solid red are derived from wild green, blue and brown discus (not Heckel discus). [16]

Description

Red turquoise discus Discus.JPG
Red turquoise discus

Like cichlids from the genus Pterophyllum (angelfish), all Symphysodon species have a laterally compressed body shape. In contrast to Pterophyllum, however, extended finnage is absent giving Symphysodon a more rounded shape. It is this body shape from which their common name, "discus", is derived. [17] The sides of the fish are frequently patterned in shades of green, red, brown, and blue. Some of the more brightly marked variants are the result of selective breeding by aquarists and do not exist in the wild. [16] [18] Discus typically reach up to 12.3–15.2 cm (4.8–6.0 in) in length, [9] [19] but captives have been claimed to reach 23 cm (9 in). [20] Adults generally weigh 150–250 g (5.3–8.8 oz). [18] No clear sexual dimorphism is seen for this fish, but males may reach a larger size than females. [18] In breeding form varieties, solid red discus (red melon, red cover) females are generally redder than males.[ citation needed ]

Behavior

Discus with two of its young nearby Discus fish with young.jpg
Discus with two of its young nearby

Symphysodon spp. are highly social, typically occurring in groups that may number many dozens of individuals, which is unique among cichlids of the Americas. [19] When breeding, the pair moves away from the group, possibly to reduce the risk of cannibalism of the young. [19] As with most cichlids, brood care is highly developed with both the parents caring for the young. [21] Additionally, adult discus produce a secretion ("discus milk") [22] through their skin, on which the larvae live during their first 4 weeks. [23] During the first two weeks, the parents stay near their young allowing them to feed easily. In the last 2 weeks, they swim away, resulting in the young being gradually "weaned off" and starting to fend for themselves. [23] Although rare in fish, more than 30 species of cichlids are known to feed their young with skin secretion to various extent, [23] including Pseudetroplus and Uaru species. [24] Sexual maturity is reached in a year. [19]

Research [25] has shown that, through this unique parental care behaviour (discus parents feeding their progeny with skin mucus), discus fish parents transmit key microorganisms to their fry. 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). [25]

Symphysodon spp. primarily feed on algae, other plant material, and detritus (periphyton), but also eat small invertebrates. Invertebrates can make up 38% of the stomach content in wild S. aequifasciatus during the high-water season, but this decreases during the low-water season, and year-round it is generally lower in the other species. [19] Unlike more predatory cichlids, Symphysodon spp. have relatively long intestines typical of a herbivore or omnivore. [19]

Distribution and habitat

A map of the range (orange shading) of Symphysodon Distribution of Symphysodon.png
A map of the range (orange shading) of Symphysodon

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. S. discus is restricted to blackwater habitats, but periodically these may experience brief floods of whitewater. [11] S. tarzoo is found in both black [11] and whitewater, [8] and S. aequifasciatus also occurs in clearwater. [11] Because of their preference for lentic habitats such as floodplains and flooded forests, whitewater inhabited by discus contains little suspended material (unlike main sections of whitewater rivers). [14]

The three species of Symphysodon have different geographic distributions. S. aequifasciatus occurs in the East Amazon downriver from the Purus Arch and S. tarzoo in the West Amazon upriver from the Purus Arch. [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. [8] [14]

The Nanay River in far western Amazonas is outside the native range; discus in this river were introduced from stock originating in the Tefé area by an aquarium exporter more than 30 years ago. [11]

A significant number of discus now live in fish farms in Southeast Asia. These discus go to home aquaria around the world. [26]

Home aquarium

Discus are kept by fishkeepers in the home aquarium, where they are valued for their striking appearance. [27] They are considered difficult to keep, due to strict requirements for water quality and the need to be kept in groups. [21] Breeders have selected for individuals with more adaptability to tap water conditions. [28]

In home aquariums, discus live for an average of 10 years, but can live up to 15 years, and can grow up to 8 inches. Like many fish in the home aquarium, they will eat almost anything that fits within their mouth. [29] Due to their size, they often require a minimum 55 US gal (210 L) – 75 US gal (280 L) aquarium. [21]

Each year the World Discus Competition takes place in Guangzhou, China. [30] The North American Discus Association focuses on both supporting hobbyists and helping to support wild discus. [31]

See also

Related Research Articles

<span class="mw-page-title-main">Cichlid</span> Family of fishes

Cichlids are fish from the family Cichlidae in the order Cichliformes. Traditionally Cichlids were classed in a suborder, the Labroidei, along with the wrasses (Labridae), in the order Perciformes, but molecular studies have contradicted this grouping. On the basis of fossil evidence, it first appeared in Argentina during the Early Eocene epoch, about 48.6 million years ago; however, molecular clock estimates have placed the family's origin as far back as 67 million years ago, during the late Cretaceous period. The closest living relative of cichlids is probably the convict blenny, and both families are classified in the 5th edition of Fishes of the World as the two families in the Cichliformes, part of the subseries Ovalentaria. This family is large, diverse, and widely dispersed. At least 1,650 species have been scientifically described, making it one of the largest vertebrate families. New species are discovered annually, and many species remain undescribed. The actual number of species is therefore unknown, with estimates varying between 2,000 and 3,000.

<span class="mw-page-title-main">Neon tetra</span> Species of fish

The neon tetra is a freshwater fish of the characin family of order Characiformes. The type species of its genus, it is native to blackwater and clearwater streams in the Amazon basin of South America. Its bright colouring makes the fish visible to conspecifics in the dark blackwater streams, and is also the main reason for its popularity among freshwater fish hobbyists, with neon tetras being one of the most widely kept tropical fish in the world.

<i>Symphysodon discus</i> Species of fish

Symphysodon discus, the red discus or Heckel discus, is a species of cichlid endemic to the Amazon Basin of Brazil, where found in the lower Rio Negro, upper Uatumã, Nhamundá, Trombetas and Abacaxis.

<i>Pterophyllum scalare</i> Species of fish

Pterophyllum scalare, most commonly referred to as angelfish or freshwater angelfish, is the most common species of Pterophyllum kept in captivity. It is native to the Amazon Basin in Peru, Colombia, and Brazil. Particularly to the Ucayali river in Peru, the Oyapock River in French Guiana, the Essequibo River in Guyana, the Solimões, the Amapá, and the Amazon rivers in Brazil. It is found in swamps or flooded grounds where vegetation is dense and the water is either clear or silty. Its native waters range from a neutral pH of 7.0 down to near 6.0, with a general water hardness (gH) range of 3 to 10 °dH, and water temperature ranging from 26 to 30 °C. This is the species of angelfish most frequently found in the aquarium trade. A similar P. scalare exists in the Rio Orinoco. They are of the same size and shape, the only difference being the stripes; the Orinoco P. scalare has thinner, but dual, stripes.

<i>Pterophyllum</i> Genus of fish

Pterophyllum is a small genus of freshwater fish from the family Cichlidae known to most aquarists as angelfish. All Pterophyllum species originate from the Amazon Basin, Orinoco Basin and various rivers in the Guiana Shield in tropical South America. The three species of Pterophyllum are unusually shaped for cichlids being greatly laterally compressed, with round bodies and elongated triangular dorsal and anal fins. This body shape allows them to hide among roots and plants, often on a vertical surface. Naturally occurring angelfish are frequently striped transversely, colouration which provides additional camouflage. Angelfish are ambush predators and prey on small fish and macroinvertebrates. All Pterophyllum species form monogamous pairs. Eggs are generally laid on a submerged log or a flattened leaf. As is the case for other cichlids, brood care is highly developed.

<i>Pterophyllum leopoldi</i> Species of fish

Pterophyllum leopoldi, also referred to as the teardrop angelfish, Leopold's angelfishdwarf angelfish, or roman-nosed angelfish, is an angelfish species native to the Amazon River, Essequibo River and Rupununi River.

<i>Geophagus</i> Genus of fishes

Geophagus is a genus of cichlids that mainly live in South America as far south as Argentina and Uruguay, but a single species, G. crassilabris is from Panama. They are found in a wide range of freshwater habitats. They are part of a group popularly known as eartheaters and mostly feed by picking up mouthfuls of sediment to sift out food items such as invertebrates, plant material and detritus. The largest species reach up to 28 cm (11 in) in standard length. They are mostly kept in aquariums.

<i>Neolamprologus brichardi</i> Species of fish

Neolamprologus brichardi is a species of cichlid endemic to the alkaline waters of Lake Tanganyika in East Africa. It is a popular aquarium fish kept in the fishkeeping hobby, where it is known under a variety of common names including Princess cichlid, Princess of Burundi, Lyretail cichlid, Fairy cichlid and Brichard's lamprologus. In addition, the species is also the subject of numerous studies on fish behaviour. It is closely related to N. pulcher from the southern half of Lake Tanganyika and some have recommended merging the two into a single species.

<span class="mw-page-title-main">Fishkeeping</span> Practice of containing fish

Fishkeeping is a popular hobby, practiced by aquarists, concerned with keeping fish in a home aquarium or garden pond. There is also a piscicultural fishkeeping industry, serving as a branch of agriculture.

<span class="mw-page-title-main">Ram cichlid</span> Species of fish

The ram cichlid is a species of freshwater fish endemic to the Orinoco River basin, in the savannahs of Venezuela and Colombia in South America. The species has been examined in studies on fish behaviour and is a popular aquarium fish, traded under a variety of common names, including ram, blue ram, German blue ram, Asian ram, butterfly cichlid, Ramirez's dwarf cichlid, dwarf butterfly cichlid and Ramirezi. The species is a member of the family Cichlidae and subfamily Geophaginae.

<span class="mw-page-title-main">Threadfin acara</span> Species of fish

The threadfin acara, also known as Heckel's thread-finned acara, is a South American species of cichlid fish. It is the only member of the genus Acarichthys and is native to rivers in the Amazon and Essequibo basins in tropical South America, and has become established in southeastern Asia. It is sometimes found in the aquarium trade.

<i>Symphysodon aequifasciatus</i> Species of fish

Symphysodon aequifasciatus, the blue discus or brown discus, is a species of cichlid native to rivers of the eastern and central Amazon Basin downriver from the Purus Arch. This discus is found in black-, clear- and whitewater, but its preference for lentic habitats such as floodplains and flooded forests means that the whitewater it inhabits contain little suspended material. It is largely restricted to water with a high temperature of 25–32 °C (77–90 °F) and a pH of 5.2–7.7.

<span class="mw-page-title-main">Orange chromide</span> A species of cichlid, indigenous to Southern India and Sri Lanka, with orange coloration.

The orange chromide is a species of cichlid fish that is endemic to freshwater and brackish streams, lagoons and estuaries in southern India and Sri Lanka. It is also known as pallathi in Malayalam. The species is popular with fishkeeping hobbyists, and is kept frequently in aquariums. The species is part of the family Cichlidae and is included in subfamily Etroplinae. The orange chromide reaches a length of up to 8 cm (3.1 in).

<i>Laetacara</i> Genus of fishes

Laetacara is a small genus of cichlids native to freshwater habitats in tropical and subtropical South America, ranging from the upper Orinoco River basin in Venezuela to the Paraná River basin Argentina. The genus is also collectively known as the smiling acaras. Like all cichlids, Laetacara species have well-developed brood care.

<i>Mesonauta</i> Genus of fishes

Mesonauta, the flag cichlids, is a small genus of cichlids native to the Amazon, Orinoco, Essequibo, Paraná and Paraguay basins in South America. Mesonauta is included in the subfamily Cichlasomatinae. They occur in various freshwater habitats such as streams and lakes, especially in areas with little water movement and aquatic vegetation. They are generally found in small groups that stay near the water surface. To avoid predators, adults may jump out of the water and juveniles mimic leaves.

<i>Symphysodon tarzoo</i> Species of fish

Symphysodon tarzoo, the green discus, is a species of cichlid endemic to Brazil; specifically, 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 stock from the Tefé region. 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. Although also known from whitewater, its preference for lentic habitats such as floodplains means that the water contain little suspended material.

<i>Mesonauta acora</i> Species of fish

Mesonauta acora is a species of cichlid fish endemic to the Amazon Basin of Brazil; specifically, to blackwater in the Xingu and Tocantins River basins in South America. The species was named by François Louis de la Porte, comte de Castelnau in 1855.

<span class="mw-page-title-main">Purus várzea</span> Ecoregion in the Amazon biome

The Purus várzea (NT0156) is an ecoregion of seasonally flooded várzea forest in the central Amazon basin. It is part of the Amazon biome. The ecoregion is home to a vegetation adapted to floods of up to 12 metres (39 ft) that may last for eight months. There is a great variety of fish and birds, but relatively fewer mammals. Ground-dwelling mammals must migrate to higher ground during the flood season. Threats include logging, cattle farming, over-fishing and mercury pollution from gold mining.

<span class="mw-page-title-main">Iquitos várzea</span>

The Iquitos várzea (NT0128) is an ecoregion of flooded forest along rivers in Brazil, Peru and Bolivia in the west of the Amazon biome. The forest is seasonally flooded up to 7 metres (23 ft) by whitewater rivers carrying nutrient-rich sediment from the Andes. The meandering rivers often shift course, creating a complex landscape of oxbow lakes, marshes, levees and bars, with grasslands, shrubs and forests in different stages of succession. During the extended flood periods fish enter the forest in search of fruit. The várzea is accessible by the navigable rivers that run through it, and has suffered from extensive deforestation to extract timber and create pasture for livestock.

References

  1. ↑ Tuccinardi, Michael (1 December 2016). "This Obscure Bangkok Market is Home to a Million-Dollar Collection of Tropical Fish. In the market for rare aquarium fish? Head to Thailand". www.AtlasObscura.com. Atlas Obscura. …Discus fish, pre-bagged for a quick sale, occupy a seller's shelves…Each tiny shop or stall usually specializes in a particular breed or category of fish or aquarium—some showcasing colorful but delicate discus and angelfish…
  2. ↑ Loiselle, Paul V. (1995). The Cichlid Aquarium. Germany: Tetra Press. ISBN   1-56465-146-0.
  3. ↑ Sands D (1994) A fishkeepers guide to Central American cichlids. Tetra Press. Belgium pg 59-60.
  4. ↑ Mills D (1993) Aquarium Fish Harper Collins ISBN   0-7322-5012-9
  5. ↑ Chong, K.; Ying, T. S.; Foo, J.; Jin, L. J.; Chong, A. (2005-09-12). "Characterisation of proteins in epidermal mucus of discus fish (Symphysodon spp.) during parental phase". Aquaculture. 249 (1–4): 469–476. doi:10.1016/j.aquaculture.2005.02.045.
  6. ↑ Discus fish - Page 5 Thomas A. Giovanetti, Matthew M. Vriends - 1991 "It was not until the 1930s and 1940s that aquarium-fish dealers began importing discus into Europe and the United States under the common name "pompadour fish." Discus are cichlids, which often surprises many aquarists."
  7. ↑ International Wildlife Encyclopedia Set - Page 2006 Robert Burton, Maurice Burton, 2002 "Popular aquarium fish because of their bright colors and attractive patterns, pompadour fish are actually quite difficult to keep and require frequent water changes. Pictured are a group of red discus, one of the two species of pompadour fish."
  8. 1 2 3 4 5 Ready, J.S.; Ferreira, E.J.G.; Kullander, S.O. (2006). "Discus fishes: mitochondrial DNA evidence for a phylogeographic barrier in the Amazonian genus Symphysodon (Teleostei: Cichlidae)". Fish Biology. 69: 200–211. doi:10.1111/j.1095-8649.2006.01232.x.
  9. 1 2 Froese, Rainer and Pauly, Daniel, eds. (2013). Species of Symphysodon in FishBase . April 2013 version.
  10. ↑ "New Discus named Symphysodon tarzoo". Matt Clarke. practical fishkeeping. 2006-11-28. Archived from the original on March 7, 2009. Retrieved 15 August 2009.
  11. 1 2 3 4 5 Bleher, H.; Stölting, K.N.; Salzburger, W.; Meyer, A. (2007). "Revision of the genus Symphysodon Heckel, 1840 (Teleostei: Perciformes: Cichlidae) based on molecular and morphological characters". Aqua. 12: 133–174.
  12. ↑ "Discus genus revised". Matt Clarke. Practical Fishkeeping. 2007-08-08. Archived from the original on 6 November 2011. Retrieved 15 August 2009.
  13. ↑ Geerts, M. (2011): On the name Symphysodon Discus Tarzoo. The Cichlid Room Companion
  14. 1 2 3 4 5 6 Amado, M.V.; Farias, I.P.; Hrbek, T. (2011). "A Molecular Perspective on Systematics, Taxonomy and Classification Amazonian Discus Fishes of the Genus Symphysodon". International Journal of Evolutionary Biology. 2011: 360654. doi: 10.4061/2011/360654 . PMC   3147135 . PMID   21811676.
  15. ↑ Eschmeyer, W.N.; Fricke, R.; van der Laan, R. (3 January 2017). "Symphysodon". Catalog of Fishes. California Academy of Sciences. Retrieved 26 January 2017.
  16. 1 2 Koh, T.L.; Khoo, G.; Fan, L.Q.; Phang, V.P.E. (1999). "Genetic diversity among wild forms and cultivated varieties of Discus (Symphysodon spp.) as revealed by Random Amplified Polymorphic DNA (RAPD) fingerprinting". Aquaculture. 173 (1): 485–497. doi:10.1016/S0044-8486(98)00478-5.
  17. ↑ Roberts, Jason (2022-03-09). "Discus Fish: The Complete Care, Species, & Breeding Guide". Build Your Aquarium. Retrieved 2022-03-11.
  18. 1 2 3 Livengood, E.J.; Ohs, C.L.; Chapman, F.A. (2009). "Candidate Species for Florida Aquaculture: Discus Symphysodon spp., a Profitable but Challenging Species for Florida Aquaculture". U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida. Retrieved 25 January 2017.
  19. 1 2 3 4 5 6 7 Crampton (2008). "Ecology and life history of an Amazon floodplain cichlid: the discus fish Symphysodon (Perciformes: Cichlidae)". Neotrop. Ichthyol. 6 (4): 599–612. doi: 10.1590/S1679-62252008000400008 .
  20. ↑ "Discus". Seriously Fish. Retrieved 25 January 2017.
  21. 1 2 3 freshwatercentral (2019-11-26). "The Complete Discus Fish Care Guide". Freshwater Central. Archived from the original on 2022-06-30. Retrieved 2019-11-26.
  22. ↑ Ball, J.N. (1969). "D. Prolactin and Epidermal Mucous Cells in Teleosts - The Endocrine System". Fish Physiology– via Sciencedirect.com.
  23. 1 2 3 Buckley, J.; Maunder, R. J.; Foey, A.; Pearce, J.; Val, A. L.; Sloman, K. A. (2010). "Biparental mucus feeding: a unique example of parental care in an Amazonian cichlid". J. Exp. Biol. 213 (22): 3787–3795. doi: 10.1242/jeb.042929 . hdl: 10026.1/12620 . PMID   21037057.
  24. ↑ Leibel, W. (2010). "Cichlids of the Americas - Mouthbrooders". FishChanel. Retrieved 22 January 2017.
  25. 1 2 Sylvain, François-Étienne; Derome, Nicolas (2017). "Vertically and horizontally transmitted microbial symbionts shape the gut microbiota ontogenesis of a skin-mucus feeding discus fish progeny". Scientific Reports. 7 (1): 5263. Bibcode:2017NatSR...7.5263S. doi:10.1038/s41598-017-05662-w. PMC   5507859 . PMID   28701764.
  26. ↑ "Build Your Dream Discus Fish Aquarium - an Expert Guide". 28 July 2018. Archived from the original on 24 May 2022. Retrieved 13 May 2019.
  27. ↑ "Aquaworld Aquarium - Article - Discus - King Of The Aquarium". www.aquaworldaquarium.com. Archived from the original on 2023-02-05. Retrieved 2019-11-26.
  28. ↑ "Discus: The whole truth and nothing but..." Practical Fishkeeping. 2016-06-13. Retrieved 2020-04-29.
  29. ↑ A-Z-Animals.com. "Discus". a-z-animals.com. Retrieved 2019-11-26.
  30. ↑ "AQUARAMA 2019 | Aquaria, Terraria, Garden & Pond | World Discus Competition". www.aquarama.com.cn. Retrieved 2019-11-26.
  31. ↑ "North American Discus Association". www.discusnada.org. Retrieved 2019-11-26.
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