goldfish

File:Goldfish in Fish Swimming Amid Falling Flowers by Liu Cai (cropped).jpg painting by Liu Cai ({{c.|1080–1120}})|alt=painting of many swimming fish, mostly in shades of tan]]

File:Carassius gibelio male 2021 G1.jpg showing lots of epithelial tubercles which appear at spawning time.]]

File:1856aquariumfresh.png.]]

[[File:Ryukin goldfish plate.jpg|thumb|Ryukin goldfish, Plate XIX in Goldfish and Their Culture in Japan, by Shinno

suke Matsubara.]]

Various species of carp (collectively known as Asian carp) have been bred and reared as food fish for thousands of years in East Asia. Some of these normally gray or silver species have a tendency to produce red, orange, or yellow color mutations; this was first recorded in Imperial China, during the Jin dynasty (266–420).{{cite web|url=http://www.oceanpark.com.hk/html/en/learning/facts/goldfish.html |title=Goldfish |publisher=Ocean Park |access-date=2009-11-16}}{{cite book|last=Roots|first=Clive|title=Domestication|year=2007|publisher=Greenwood Press|location=Westport|isbn=978-0-313-33987-5|pages=20–21}}

During the Tang dynasty (AD 618–907), it was popular to raise carp in ornamental ponds and water gardens. A natural genetic mutation produced gold (actually yellowish orange) rather than silver coloration. People began to selectively breed the gold variety instead of the silver variety, keeping them in ponds or other bodies of water. On special occasions at which guests were expected, they would be moved to a much smaller container for display.[http://www.hagen.com/pdf/aquatic/Nutrafin_No4_English.pdf Nutrafin Aquatic News, Issue #4] {{Webarchive|url=https://web.archive.org/web/20070413152258/http://www.hagen.com/pdf/aquatic/Nutrafin_No4_English.pdf |date=2007-04-13 }}, 2004, Rolf C. Hagen, Inc. (USA) and Rolf C. Hagen Corp. (Montreal, Canada)

By the Song dynasty (AD 960–1279), the selective domestic breeding of goldfish was firmly established.{{cite book|last=Smartt|first=Joseph|title=Goldfish varieties and genetics: A handbook for breeders|url=https://archive.org/details/goldfishvarietie00smar|url-access=limited|year=2001|publisher=Blackwell Science|location=Oxford|isbn=978-0-85238-265-3|page=[https://archive.org/details/goldfishvarietie00smar/page/n30 21]}} In 1162, the empress of the Song dynasty ordered the construction of a pond to collect the red and gold variety. By this time, people outside the imperial family were forbidden to keep goldfish of the gold (yellow) variety, yellow being the imperial color.{{Cite journal |last1=Chen |first1=Duo |last2=Zhang |first2=Qing |last3=Tang |first3=Weiqi |last4=Huang |first4=Zhen |last5=Wang |first5=Gang |last6=Wang |first6=Yongjun |last7=Shi |first7=Jiaxian |last8=Xu |first8=Huimin |last9=Lin |first9=Lianyu |last10=Li |first10=Zhen |last11=Chi |first11=Wenchao |last12=Huang |first12=Likun |last13=Xia |first13=Jing |last14=Zhang |first14=Xingtan |last15=Guo |first15=Lin |date=2020-11-24 |title=The evolutionary origin and domestication history of goldfish ( Carassius auratus ) |journal=Proceedings of the National Academy of Sciences |language=en |volume=117 |issue=47 |pages=29775–29785 |doi=10.1073/pnas.2005545117 |doi-access=free |issn=0027-8424 |pmc=7703540 |pmid=33139555|bibcode=2020PNAS..11729775C }}

During the Ming dynasty (1368–1644), goldfish also began to be raised indoors, which permitted selection for mutations that would not be able to survive in ponds. The first occurrence of -tailed goldfish was recorded in the Ming dynasty. In 1603, goldfish were introduced to Japan. In 1611, goldfish were introduced to Portugal and from there to other parts of Europe.{{cite web | url=http://www.bristol-aquarists.org.uk/goldfish/info/info.htm | title=Background information about goldfish | publisher=Bristol Aquarists' Society | access-date=2006-07-28}}

During the 1620s, goldfish were highly regarded in southern Europe because of their metallic scales, and symbolized good luck and fortune. It became a tradition for married men to give their wives a goldfish on their first anniversary, as a symbol for the prosperous years to come. This tradition quickly died, as goldfish became more available, losing their status. Goldfish were first introduced to North America around 1850 and quickly became popular in the United States.{{cite book | last = Brunner | first = Bernd | title = The Ocean at Home | publisher = Princeton Architectural Press | year = 2003 | location = New York | isbn = 978-1-56898-502-2 | url-access = registration | url = https://archive.org/details/oceanathomeil00brun }}{{cite book|last=Mulertt |first=Hugo |title=The Goldfish And Its Systematic Culture With A View To Profit |year=1883|url=https://archive.org/details/goldfishitssyste00mule |access-date=2009-07-07|publisher=Cincinnati [McDonald & Eick, print.] }}

File:CarassiusCarassius8.JPG, around 6 months old, 7 cm, from Haarlem, Netherlands.]]

There has been considerable debate about the taxonomy of the goldfish. Previously, the goldfish was believed to be either a subspecies of the crucian carp (Carassius carassius), or of the Prussian carp (Carassius gibelio).{{cite web |last1=Laboratory |first1=NOAA Great Lakes Environmental Research |title=NOAA National Center for Research on Aquatic Invasive Species (NCRAIS) |url=https://nas.er.usgs.gov/queries/greatlakes/FactSheet.aspx?SpeciesID=508&Potential=N&Type=0 |website=nas.er.usgs.gov |access-date=16 December 2020}}{{cite journal|last=Komiyama |first=Tomoyoshi |author2=Hiroyuki Kobayashi |author3=Yoshio Tateno |author4=Hidetoshi Inoko |author5=Takashi Gojobori |author6=Kazuho Ikeo |title=An evolutionary origin and selection process of goldfish |journal=Gene |date=February 2009 |volume=430 |issue=1–2|pmid=19027055 |pages=5–11 |doi=10.1016/j.gene.2008.10.019}}{{cite web|title=Common Gold Fish |work=Aquarticles |author=Les Pearce |url=http://www.aquarticles.com/articles/ponds/Pearce_Common_Goldfishhtml.htm |access-date=20 June 2006 |url-status=dead |archive-url=https://web.archive.org/web/20060528173947/http://www.aquarticles.com/articles/ponds/Pearce_Common_Goldfishhtml.htm |archive-date=28 May 2006 }} However, modern genetic sequencing has suggested otherwise, and that modern goldfish are domesticated varieties of C. auratus that are native to Southern China.{{cite journal|last=Wang |first=Shu-Yan |author2=Jing Luo |author3=Robert W. Murphy |author4=Shi-Fang Wu |author5=Chu-Ling Zhu |author6=Yun Gao |author7=Ya-Ping Zhang |title=Origin of Chinese Goldfish and Sequential Loss of Genetic Diversity Accompanies New Breeds |journal=PLOS ONE |date=19 March 2013 |volume=430 |issue=3 |pages=e59571 |doi=10.1371/journal.pone.0059571|pmid=23527220 |pmc=3602300 |bibcode=2013PLoSO...859571W |doi-access=free }} C. auratus are differentiated from other Carassius species by several characteristics. C. auratus have a more pointed snout, while the snout of C. carassius is well rounded. C. gibelio often has a grayish/greenish color, while crucian carp are always golden bronze. Juvenile crucian carp have a black spot on the base of the tail, which disappears with age. In C. auratus, this tail spot is never present. C. auratus have fewer than 31 scales along the lateral line, while crucian carp have 33 scales or more.

Goldfish can hybridize with some other Carassius species of carp. Koi and common carp may also interbreed with goldfish to produce sterile hybrids.

Wild goldfish typically grow to between 4.7 inches (12 cm) and 8.7 inches (22 cm) but can reach 16 inches (41 cm).{{Cite book |last1=Page |first1=Lawrence M. |title=A field guide to freshwater fishes: North America north of Mexico |last2=Burr |first2=Brooks M. |date=1991 |publisher=Houghton Mifflin |others=National Audubon Society, National Wildlife Foundation, Roger Tory Peterson Institute |isbn=978-0-395-35307-3 |series=The Peterson field guide series |location=Boston}} The size of pet goldfish depends upon its breed.{{Cite web |title=Goldfish history, colour and finnage, diseases, how to keep them, and how to breed them |url=https://www.bristol-aquarists.org.uk/goldfish/info/info.htm |access-date=2024-02-05 |website=www.bristol-aquarists.org.uk}}

As of April 2008, the largest goldfish in the world was believed by the BBC to measure {{convert|19|in|cm}}, in the Netherlands.{{cite news|url=http://news.bbc.co.uk/1/hi/england/kent/7352909.stm |title=Giant goldfish 'simply amazing' |work=BBC News |date=17 April 2008 |access-date=17 July 2010}} At the time, a goldfish named "Goldie", kept as a pet in a tank in Folkestone, England, was measured as {{convert|15|in|cm}} and over {{convert|2|lb|kg}}, and named as the second largest in the world behind the Netherlands fish. The secretary of the Federation of British Aquatic Societies (FBAS) stated of Goldie's size, "I would think there are probably a few bigger goldfish that people don't think of as record holders, perhaps in ornamental lakes". In July 2010, a goldfish measuring {{convert|16|in|cm}} and {{convert|5|lb|kg}} was caught in a pond in Poole, England, thought to have been abandoned there after outgrowing a tank.{{cite news|url=https://www.bbc.co.uk/news/uk-england-10649008 |title=Surrey schoolboy catches 5lb goldfish in Dorset lake |work=BBC News |date=15 July 2010 |access-date=17 July 2010}} On November 16, 2020, a {{convert|15|in|cm|adj=on}} goldfish weighing {{convert|9|lb}} was found in a {{cvt|16|acre|ha}} lake in Greenville, South Carolina, while conducting a population survey of Oak Grove Lake.{{Cite web|title='Massive' goldfish weighing 9 pounds found in South Carolina lake|url=https://www.nbcnews.com/news/us-news/massive-goldfish-weighing-9-pounds-found-south-carolina-lake-n1250396|access-date=2021-05-17|website=NBC News|date=8 December 2020 |language=en}}

As a domestic fish, thus an easily accessible model organism, goldfish have one of the most studied senses of vision in fishes.{{cite book |title=Sensory Processing in Aquatic Environments |url=https://archive.org/details/sensoryprocessin00bull |url-access=limited |last=Neumeyer |first=C.|editor=Collin, S.P. |editor2=Marshall, N.J. |chapter=Color Vision in Fishes and Its Neural Basis |year=2003|publisher=Springer-Verlag |location=New York |page=[https://archive.org/details/sensoryprocessin00bull/page/n253 223]|isbn=9780387955278}} Goldfish have four kinds of cone cells, which are respectively sensitive to different colors: red, green, blue and ultraviolet. The ability to distinguish between four different primary colors classifies them as tetrachromats.{{cite book| last = Neumeyer| first = Christa | title = Das Farbensehen des Goldfisches: Eine verhaltensphysiologische Analyse|year = 1988| publisher = G. Thieme| isbn = 978-3137187011}}

Goldfish have one of the most studied senses of hearing in fish.Ladich, F., & Fay, R. R. (2013). Auditory evoked potential audiometry in fish. Reviews in Fish Biology and Fisheries, 23(3), 317–364. They have two otoliths, permitting the detection of sound particle motion, and Weberian ossicles connecting the swim bladder to the otoliths, facilitating the detection of sound pressure.Fay, R. R., & Popper, A. N. (1974). Acoustic stimulation of the ear of the goldfish (Carassius auratus). Journal of Experimental Biology, 61(1), 243–260.

File:Goldfisheggs.JPG

File:Goldfishfry.JPG

Goldfish can only grow to sexual maturity with enough water and the right nutrition. Most goldfish breed in captivity, particularly in pond settings. Breeding usually happens after a significant temperature change, often in spring. Males chase gravid female goldfish (females carrying eggs), and prompt them to release their eggs by bumping and nudging them.

Goldfish, like all cyprinids, are egg-layers. Their eggs are adhesive and attach to aquatic vegetation, typically dense plants such as Cabomba or Elodea or a spawning mop. The eggs hatch within 48 to 72 hours.

Within a week or so, the fry begins to assume its final shape, although a year may pass before they develop a mature goldfish color; until then they are a metallic brown like their wild ancestors. In their first weeks of life, the fry grow quickly—an adaptation born of the high risk of getting devoured by the adult goldfish (or other fish and insects) in their environment.{{Cite web|url=http://thefishvet.com.au/pdf/Care_Gf_byRL.pdf|title=Goldfish (Carassius auratus)|first=Richmond|last=Loh|publisher=The Fish Vet.com|access-date=December 31, 2013|archive-date=January 27, 2014|archive-url=https://web.archive.org/web/20140127141326/http://thefishvet.com.au/pdf/Care_Gf_byRL.pdf|url-status=dead}}

Some highly selectively bred goldfish can no longer breed naturally due to their altered shape. The artificial breeding method called "hand stripping" can assist in breeding, but can harm the fish if not done correctly.{{Cite web |date=1991 |title=Techniques for Taking and Fertilizing the Spawn of Fish |url=https://fisheries.tamu.edu/files/2013/09/SRAC-Publication-No.-426-Techniques-for-Taking-and-Fertilizing-the-Spawn-of-Fish.pdf |access-date=February 5, 2024}} In captivity, adults may also eat young that they encounter.

Goldfish are able to survive short periods of entirely anoxic conditions. Survival is shorter under higher temperatures, suggesting that this is a cold weather adaptation. Researchers speculate that this is specifically an adaptation to survival in frozen water bodies over winter.

Energy is obtained from liver glycogen. This process depends upon a pyruvate decarboxylase – the first known in vertebrates.{{ Cite journal | url=http://cdnsciencepub.com/doi/10.1139/z77-170 | title=Walker, R. M., & Johansen, P. H. (1977). Anaerobic metabolism in goldfish (Carassius auratus). Canadian Journal of Zoology, 55(8), 1304–1311. doi:10.1139/z77-170 | year=1977 | doi=10.1139/z77-170 | pmid=902178 | last1=Walker | first1=R. M. | last2=Johansen | first2=P. H. | journal=Canadian Journal of Zoology | volume=55 | issue=8 | pages=1304–11 | url-access=subscription }}{{ Cite journal | url= | title=Fagernes, C.E., Stensløkken, K., Røhr, Å.K. et al. Extreme anoxia tolerance in crucian carp and goldfish through neofunctionalization of duplicated genes creating a new ethanol-producing pyruvate decarboxylase pathway. Sci Rep 7, 7884 (2017). DOI: 10.1038/s41598-017-07385-4 | year=2017 | doi=10.1038/s41598-017-07385-4 | pmid=28801642 | last1=Fagernes | first1=C. E. | last2=Stensløkken | first2=K. O. | last3=Berenbrink | first3=M. | last4=Ellefsen | first4=S. | last5=Nilsson | first5=G. E. | journal=Scientific Reports | volume=7 | issue=1 | page=7884 | pmc=5554223 }}

Although they are a freshwater fish, goldfish have been found in brackish water with a salinity of 17.{{ Cite journal | title=Tweedley, J.R., Hallett, C.S. & Beatty, S.J. Baseline survey of the fish fauna of a highly eutrophic estuary and evidence for its colonisation by Goldfish (Carassius auratus). Int Aquat Res 9, 259–270 (2017). DOI: 10.1007/s40071-017-0174-1 | journal=International Aquatic Research | date=September 2017 | volume=9 | issue=3 | pages=259–270 | doi=10.1007/s40071-017-0174-1 | s2cid=59358196 | last1=Tweedley | first1=James R. | last2=Hallett | first2=Chris S. | last3=Beatty | first3=Stephen J. | doi-access=free }}

Goldfish are gregarious, displaying schooling behavior, as well as displaying the same types of feeding behaviors.

Goldfish have learned behaviors, both as groups and as individuals, that stem from native carp behavior. They are a generalist species with varied feeding, breeding, and predator avoidance behaviors that contribute to their success. As fish, they can be described as "friendly" towards each other. Very rarely does a goldfish harm another goldfish, nor do the males harm the females during breeding. The only real threat that goldfish present to each other is competing for food. Commons, comets, and other faster varieties can easily eat all the food during a feeding before varieties can reach it. This can lead to stunted growth or possible starvation of fancier varieties when they are kept in a pond with their single-tailed brethren. As a result, care should be taken to combine only breeds with similar body type and swim characteristics.

Goldfish have strong associative learning abilities, as well as social learning skills. In addition, their visual acuity allows them to distinguish between individual humans. Owners may notice that fish react favorably to them (swimming to the front of the glass, swimming rapidly around the tank, and going to the surface mouthing for food) while hiding when other people approach the tank. Over time, goldfish learn to associate their owners and other humans with food, often "begging" for food whenever their owners approach.{{Cite web |last=Plumer |first=Brad |date=2016-06-09 |title=This is unsettling: fish can recognize human faces |url=https://www.vox.com/2016/6/9/11889508/fish-facial-recognition |access-date=2024-02-05 |website=Vox |language=en}}

Goldfish that have constant visual contact with humans also stop considering them to be a threat. After being kept in a tank for several weeks, sometimes months, it becomes possible to feed a goldfish by hand without it shying away.

Goldfish have a memory-span of at least three months and can distinguish between different shapes, colors, and sounds.Research by the School of Psychology at the University of Plymouth in 1994. Goldfish were trained to push a lever to earn a food reward; when the lever was fixed to work only for an hour a day, the fish soon learned to activate it at the correct time. See: {{Cite journal | date=July 1994 | title=Temporal discrimination learning of operant feeding in goldfish | journal=Journal of the Experimental Analysis of Behavior | volume=62 | issue=1 | pmid=16812735 | pmc=1334363 | pages=1–13 | last1 = Gee | first1 = P | last2 = Stephenson | first2 = D | last3 = Wright | first3 = DE | doi=10.1901/jeab.1994.62-1}}The Discovery Channel's show MythBusters tested the contemporary legend that goldfish only had a memory span of three seconds and were able to prove that goldfish had a longer memory span than commonly believed. The experiment involved training the fish to navigate a maze. It was evident that they were able to remember the correct path of the maze after more than a month. {{usurped|1=[https://web.archive.org/web/20070626043452/http://mythbustersresults.com/episode11 MythBuster Results: A goldfish’s memory lasts only three seconds]}} By using positive reinforcement, goldfish can be trained to recognize and to react to light signals of different colorsDemonstrated in a 1994 public experiment at the Palais de la Découverte science museum. The experimental details and results are described in: {{Cite journal

| date=April 1994

| title=Poissons rouges: la mémoire dans l'eau

| journal=Revue du Palais de la Découverte

| volume=217

}} or to perform tricks.{{cite web |url= https://abcnews.go.com/story?id=4803721|title=Send Your Fish to School

|date=May 7, 2008|work=ABC News|access-date=December 28, 2012}} Fish respond to certain colors most evidently in relation to feeding. Fish learn to anticipate feedings provided they occur at around the same time every day.

{{Main|List of goldfish varieties}}

As with many other examples of animal, selective breeding of goldfish over centuries has produced several color variations, some of them far removed from the "golden" color of the original fish. There are also different body shapes, and fin and eye configurations. Some extreme versions of the goldfish live only in aquariums—they are much less hardy than varieties closer to the "wild" original. However, some variations are hardier, such as the Shubunkin. Currently, there are about 300 breeds recognized in China. The vast majority of goldfish breeds today originated from China. Some of the main varieties are:

Chinese tradition classifies goldfish into four main types.{{Cite web |url=http://www.cnaquafish.com/html_news/QiYeXinWenTest-2-3.html |title=Evolution and Varieties of Goldfish |access-date=2015-08-02 |archive-url=https://web.archive.org/web/20160110164203/http://www.cnaquafish.com/html_news/QiYeXinWenTest-2-3.html |archive-date=2016-01-10 |url-status=dead }} These classifications are not commonly used in the West.

• Crucian (also called "grass") — Goldfish without anatomical features, similar to Crucian carp or grass carp except for their coloration. These include the common goldfish, comet goldfish and Shubunkin.
• Wen — Goldfish having a tail, e.g., fantails and veiltails. "Wen" is also the name of the characteristic headgrowth on such strains as oranda and lionhead.
• Dragon Eye — Goldfish having extended eyes, e.g., black moor, bubble eye, and telescope eye
• Egg — Goldfish having no dorsal fin, usually with an 'egg-shaped' body, e.g., lionhead. This group includes a bubble eye without a dorsal fin.

File:Pool Fisheries 01.jpg]]

File:Goldfish Matisse.jpg by Henri Matisse, 1912]]

Like most species in the carp family, goldfish produce a large amount of waste both in their feces and through their gills, releasing harmful chemicals into the water. Buildup of this waste to toxic levels can occur in a relatively short period of time, and can easily cause a goldfish's death. For common and comet varieties, each goldfish should have about {{convert|20|usgal}} of water. Smaller fantail goldfish should have about {{convert|10|usgal}} per goldfish. The water surface area determines how much oxygen diffuses and dissolves into the water. A general rule is have {{convert|1|sqft}}. Active aeration by way of a water pump, filter or fountain effectively increases the surface area agitation.

The goldfish is classified as a coldwater fish, and can live in unheated aquaria at a temperature comfortable for humans. However, rapid changes in temperature, for example in an office building in winter when the heat is turned off at night, can kill them, especially if the tank is small. Care must also be taken when adding water, as the new water may be of a different temperature. Temperatures under about {{convert|10|C|F}} are dangerous to fancy varieties, though commons and comets can survive slightly lower temperatures. Extremely high temperatures (over {{convert|30|C|F}}) can also harm goldfish. However, higher temperatures may help fight protozoan infestations by accelerating the parasite's life cycle—thus eliminating it more quickly. The optimum temperature for goldfish is between {{convert|20|and|22|C|F}}.{{cite web |url=http://www.mypets.net.au/flex/goldfish/528/1 |title=Goldfish |publisher=Mypets.net.au |access-date=2011-11-19 |archive-date=2010-07-28 |archive-url=https://web.archive.org/web/20100728043700/http://www.mypets.net.au/flex/goldfish/528/1 |url-status=dead }}

Like all fish, goldfish do not like to be petted. In fact, touching a goldfish can endanger its health, because it can cause the protective slime coat to be damaged or removed, exposing the fish's skin to infection from bacteria or water-borne parasites. However, goldfish respond to people by surfacing at feeding time, and can be trained or acclimated to taking pellets or flakes from human fingers. The reputation of goldfish dying quickly is often due to poor care.{{cite web|url=http://www.experiencefestival.com/goldfish |title=Goldfish |publisher=Experiencefestival.com |access-date=2011-11-19 |url-status=dead |archive-url=https://web.archive.org/web/20111212210227/http://www.experiencefestival.com/goldfish |archive-date=2011-12-12 }} The lifespan of goldfish in captivity can extend beyond 10 years.{{Cite news | url=https://www.bbc.com/news/29210991 | title=Goldfish has brain operation| work=BBC News| date=2014-09-15}}

If left in the dark for a period of time, goldfish gradually change color until they are almost gray.{{Cite web |date=2021-08-25 |title=Frequent question: Why do Goldfish Change Color? |url=https://www.nativefish.org/frequent-question-why-do-goldfish-change-color/ |access-date=2024-02-05 |website=Native Fish |language=en-US}} Goldfish produce pigment in response to light, similarly to how human skin becomes tanned in the sun. Fish have cells called chromatophores that produce pigments that reflect light and give the fish coloration. The color of a goldfish is determined by their diet, water quality, and exposure to light, along with age and health.

Because goldfish eat live plants, their presence in a planted aquarium can be problematic. Only a few aquarium plant species, such as Cryptocoryne and Anubias, can survive around goldfish, but they require special attention so that they are not uprooted.{{Cite web |title=Planted Tanks for Goldfish |url=https://injaf.org/aquarium-fish/the-goldfish-section/planted-tanks-for-goldfish/ |access-date=2024-02-05 |website=INJAF |language=en-US}}

File:Fish pond with filter Bury England 8 May 2023.jpg]]

File:Red Oranda goldfish in outdoor pond.jpg

Goldfish are popular pond fish, since they are small, inexpensive, colorful, and very hardy. In an outdoor pond or water garden, they may even survive for brief periods if ice forms on the surface, as long as there is enough oxygen remaining in the water and the pond does not freeze solid. Common, London and Bristol shubunkins, jikin, wakin, comet and some hardier fantail goldfish can be kept in a pond year-round in temperate and subtropical climates. Moor, veiltail, oranda and lionhead can be kept safely in outdoor ponds year-round only in more tropical climates and elsewhere only in summer months.

Compatible fish include rudd, tench, orfe and koi, but the last require specialized care. Ramshorn snails are helpful by eating any algae that grows in the pond. Without some form of animal population control, goldfish ponds can easily become overstocked. Fish such as orfe consume goldfish eggs.

Ponds small and large are fine in warmer areas, though goldfish can "overheat" in small volumes of water in the summer in tropical climates.{{cn|date=October 2024}} In frosty climes, the depth should be at least {{convert|80|cm|in|sp=us}} to preclude freezing. During winter, goldfish become sluggish, stop eating and often stay on the bottom of the pond. This is normal; they become active again in the spring. Unless the pond is large enough to maintain its own ecosystem without interference from humans, a filter is important to clear waste and keep the pond clean. Plants are essential as they act as part of the filtration system, as well as a food source for the fish. Plants are further beneficial since they raise oxygen levels in the water.

Like their wild ancestors, common and comet goldfish as well as shubunkin can survive, and even thrive, in any climate that can support a pond. In general, when released into the wild, goldfish quickly take over the waterways as an invasive species.{{Cite web |title=Goldfish |url=https://www.invasivespeciescentre.ca/invasive-species/meet-the-species/fish-and-invertebrates/goldfish/ |access-date=2024-02-05 |website=Invasive Species Centre |language=en-CA}}{{Cite news |last=Yin |first=Steph |date=2016-09-22 |title=In the Wild, Goldfish Turn From Pet to Pest |url=https://www.nytimes.com/2016/09/23/science/discarded-goldfish-invasive-species.html |access-date=2024-02-05 |work=The New York Times |language=en-US |issn=0362-4331}}

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{{See also|Fish food}}

In the wild, the diet of goldfish consists of crustaceans, insects, and various plant matter. Like most fish, they are opportunistic feeders and do not stop eating on their own accord. Overfeeding can be deleterious to their health, typically by blocking the intestines. This happens most often with selectively bred goldfish, which have a convoluted intestinal tract. When excess food is available, they produce more waste and feces, partly due to incomplete protein digestion. Overfeeding can sometimes be diagnosed by observing feces trailing from the fish's cloaca.

Goldfish-specific food has less protein and more carbohydrate than conventional fish food. Enthusiasts may supplement this diet with shelled peas (with outer skins removed), blanched green leafy vegetables, and bloodworms. Young goldfish benefit from the addition of brine shrimp to their diet. As with all animals, goldfish preferences vary.

Like some other well-known aquarium fish, such as the guppy and mosquitofish, goldfish (and other carp) are frequently added to stagnant bodies of water in an attempt to reduce mosquito populations, which spread the vectors of diseases such as West Nile virus, malaria, and dengue. However, introducing goldfish has often had negative consequences for local ecosystems,{{cite book|url=https://books.google.com/books?id=lNkwt3gX-2cC&q=goldfish+released+into+the+wild&pg=PA154|title=Biotechnology Deskbook|author1=William L. Arnold|author2=William L. Anderson|page=154|year=2001|publisher=Environmental Law Institute|isbn=978-1-58576-029-9}} and their efficacy as pest control has never been compared to those of native fishes.

The market for live goldfish and other crucian carp usually imported from China was $1.2{{nbsp}}million in 2018. Some high quality varieties cost between $125 and $300.{{cite news |last=Selyukh |first=Alina |url=https://www.npr.org/2019/10/16/768553956/the-goldfish-tariff-fancy-pet-fish-among-the-stranger-casualties-of-the-trade-wa |title=The Goldfish Tariff: Fancy Pet Fish Among The Stranger Casualties Of The Trade War |work=NPR |date=2019-10-16 |access-date=2019-10-17 }}

File:Goldfish Scooped Up.jpg]]

Fishbowls are detrimental to the health of goldfish and are prohibited by animal welfare legislation in several municipalities.{{cite news | url=http://www.timesonline.co.uk/article/0,,13509-1844070,00.html | archive-url=https://archive.today/20060105045820/http://www.timesonline.co.uk/article/0,,13509-1844070,00.html | url-status=dead | archive-date=January 5, 2006 | title=Rome bans goldfish bowls, orders dog owners on walks – World – Times Online | access-date=2006-07-21 | location=London | work=The Times | first1=Sam | last1=Knight | date=2005-10-26}}{{cite news | url=http://www.abc.net.au/news/2004-07-24/council-bans-goldfish-bowls/2014352 | title=Council bans goldfish bowls | access-date=2015-04-21 | work=ABC Australian Broadcast Corporation | date=2004-07-23}} The practice of using bowls as permanent fish housing originated from a misunderstanding of Chinese "display" vessels: goldfish which were normally housed in ponds were, on occasion, temporarily displayed in smaller containers to be better admired by guests.

Goldfish kept in bowls or "mini-aquariums" suffer from death, disease, and stunting, due primarily to the low oxygen and very high ammonia/nitrite levels inherent in such an environment.{{cite web|url=http://goldfishcareguide.com/2008/03/05/5-reasons-not-to-use-goldfish-bowls/|title=5 reasons not to use goldfish bowls|access-date=2009-02-01|date=2008-03-05|publisher=Goldfish Care Guide|archive-url=https://web.archive.org/web/20180525162142/http://goldfishcareguide.com/2008/03/05/5-reasons-not-to-use-goldfish-bowls/|archive-date=2018-05-25|url-status=dead}} In comparison to other common aquarium fish, goldfish have high oxygen needs and produce a large amount of waste due to the fact they lack a stomach;{{cite web|url= https://injaf.org/aquarium-fish/the-goldfish-section/goldfish-and-their-diet/ | title=goldie

|accessdate=1 February 2022|work=goldfishsection}} therefore they require a substantial volume of well-filtered water to thrive. In addition, all goldfish varieties have the potential to reach {{convert|5|in}} in total length, with single-tailed breeds often exceeding {{convert|1|ft}}. Single-tailed varieties include common and comet goldfish.

In many countries, carnival and fair operators commonly give goldfish away in plastic bags as prizes. In late 2005 Rome banned the use of goldfish and other animals as carnival prizes. Rome has also banned the use of "goldfish bowls", on animal cruelty grounds, as well as Monza, Italy, in 2004. In the United Kingdom, the government proposed banning this practice as part of its Animal Welfare Bill,{{cite web|url=http://www.defra.gov.uk/animalh/welfare/bill/index.htm |title=Defra, UK – Animal Health and Welfare – Animal Welfare – Animal Welfare Bill |access-date=2006-07-21 |url-status=dead |archive-url=https://web.archive.org/web/20060820191520/http://www.defra.gov.uk/animalh/welfare/bill/index.htm |archive-date=2006-08-20 }}

BBC News Online - [http://news.bbc.co.uk/1/hi/magazine/3893889.stm Goldfish are no longer to be given as prizes] though this has since been amended to only prevent goldfish being given as prizes to unaccompanied minors.

BBC News Online - [http://news.bbc.co.uk/1/hi/uk_politics/4174457.stm Ban on goldfish prizes 'dropped']

In Japan, during summer festivals and religious holidays (ennichi), a traditional game called goldfish scooping is played, in which a player scoops goldfish from a basin with a special scooper. Sometimes bouncy balls are substituted for goldfish.

Although edible and closely related to some fairly widely eaten species, goldfish are rarely eaten. A fad among American college students for many years was swallowing goldfish as a stunt and as a fraternity initiation process. The first recorded instance was in 1939 at Harvard University.{{cite web|url=http://library.thinkquest.org/3205/SwalG.html |title=Swallowing Goldfish |access-date=2006-07-21 |url-status=dead |archive-url=https://web.archive.org/web/20060618034748/http://library.thinkquest.org/3205/SwalG.html |archive-date=2006-06-18 }} The practice gradually fell out of popularity over the course of several decades and is rarely practiced today.

Some animal advocates have called for boycotts of goldfish purchases, citing industrial farming and low survival rates of the fish.{{cite web|url=https://greenprophet.com/2012/03/goldfish-nowruz-iranian-new-year/|title=5 Million Goldfish Die for Nowruz – the Iranian New Year|first=Tafline|last=Laylin|website=Green Prophet|date=2012-03-19}}{{cite web|url=https://globalvoices.org/2012/03/16/iran-a-nowruz-new-year-without-goldfish/|title=Iran: A Nowruz New Year Without Goldfish? · Global Voices|date=16 March 2012}}

{{seealso|The Golden-Headed Fish|The Tale of the Fisherman and the Fish|The Gold-Children}}

File:Nowrooz-Yousef_Abdinejad-50x70cm-oil_on_canvas.jpg

In Chinese history, goldfish was seen "as a symbol of luck and fortune". Moreover, only members of the Song dynasty could own goldfish.{{Cite web |last=Gulliver |first=Katrina |date=2012-11-01 |title=The Great Goldfish Invasion: How an Exotic Carp Took Over America |url=https://www.theatlantic.com/national/archive/2012/11/the-great-goldfish-invasion-how-an-exotic-carp-took-over-america/264420/ |access-date=2024-02-05 |website=The Atlantic |language=en}} In Iran and among the international Iranian diaspora, goldfish is a traditional part of Nowruz celebrations. Goldfish are usually placed on Haft-sin tables as a symbol of progress.{{Cite web|title=Nowruz: Persian New Year's Table Celebrates Spring Deliciously|url=https://www.npr.org/sections/thesalt/2016/03/20/471174857/nowruz-persian-new-years-table-celebrates-spring-deliciously|access-date=2021-03-24|website=NPR.org|date=20 March 2016 |language=en|last1=Fulton |first1=April |last2=Ardalan |first2=Davar }}

• Aquaculture
• List of goldfish varieties
• Henri Matisse and goldfish

{{Reflist|30em}}

{{Commons}}

• {{ITIS |id=163350 |taxon=Carassius auratus |access-date=5 October 2004}}
• {{FishBase_species alt|ID=271|taxon=Carassius auratus auratus|year=2004|month=September}}
• [https://goldfishmania.com/goldfish-types/ Goldfish Types] {{Webarchive|url=https://web.archive.org/web/20221207015905/https://goldfishmania.com/goldfish-types/ |date=2022-12-07 }} — Description of 50 plus varieties of goldfish with pictures
• [http://www.bristol-aquarists.org.uk/goldfish/goldfish.htm Bristol Aquarists' Society: Goldfish] — Photographs and descriptions of the different goldfish varieties

{{Goldfish breeds}}

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Category:Fish described in 1758

Category:Taxa named by Carl Linnaeus

Category:Carassius

Category:Fishkeeping

Category:Fish of China