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Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Genus: Carassius
Species: C. auratus
Subspecies: C. a. auratus
Trinomial name
Carassius auratus auratus
( Linnaeus, 1758)
The goldfish (Carassius auratus auratus) was one of the earliest fish to be domesticated, and is still one of the most commonly kept aquarium fish. A relatively small member of the carp family (which also includes the koi carp and the crucian carp), the goldfish is a domesticated version of a dark-gray/olive/brown carp native to East Asia (first domesticated in China) that was introduced to Europe in the late 17th century. It may grow to a maximum length of 23 inches (59 cm) and a maximum weight of 6.6 lb (3.0 kg), although this is rare; most individual goldfish grow to under half this size. In optimal conditions goldfish may live more than 20 years (the world record is 41 years); however, most household goldfish will only live six to eight years because owners keep them in tanks under the size of 40 US gallons.

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Aquarium conditions
Native Environment
Varieties of domesticated goldfish
Goldfish in ponds
Wild Goldfish and relationship to Crucian carp
Mosquito control
Edibility and cruelty

History - Contents

During the Tang Dynasty, it was popular for Chinese ponds to have carps. As the result of a genetic mutation one of these carp displayed "gold" (actually yellowish orange) rather than silver coloration. This mutation is associated with a dominant gene which also makes the breeding of this trait rather easy. The gold-coloured strain became popular for keeping in containers. Afterwards, the people began to breed the gold variety instead of the silver, and began to keep them into small containers to watch.In AD 1162 the Empress ordered the building of a pond to collect the red and gold variety of those carps. By this time people outside the royal family were forbidden to keep gold fishes. An order was given to the keepers to kill all the fish that were gold in colour because yellow was the royal colour and the court was offended. This is why there are more orange goldfish than yellow goldfish, even though genetically yellow is easier to breed for.As bred in captivity, more mutations occurred producing more colours and fancy goldfish appeared. According to old books, the occurrence of other colours were first recorded in AD 1276. In the Ming Dynasty it was recorded the first occurrence of fancy tailed goldfish. In AD 1502, goldfish were introduced to Japan, where it had been developed the Ryukin and Tosakin varieties.In AD 1611, Goldfish were introduced to Portugal, the starting point from which they were introduced to other parts of Europe. The goldfish was finally introduced to North America in AD 1874.

Aquarium conditions - Contents

The goldfish is quite hardy which accounts for part of its popularity. Their supposed reputation in some areas for dying quickly is often due to poor care amongst uninformed buyers, especially children, looking for a "cheap" pet. The goldfish is a cold-water fish, and can live in an unheated aquarium or in an outdoor water garden. In a pond, it will even survive brief periods of ice forming on the surface, so long as there is enough oxygen remaining in the water and the pond does not freeze solid.Like most carp, goldfish produce a large amount of waste both in the feces and through their gills, releasing harmful chemicals in the water. This also happens because goldfishes cannot digest an excess of proteins, unlike most tropical fish. Build-up of this waste to toxic levels can occur in a relatively short period of time, often the cause of a fish's sudden death. Although goldfish were historically displayed in small "goldfish bowls", a healthy and happy goldfish requires at least 40 US gallons (150 litres) of water in order to live a full life. Each additional fish requires an additional 40 gallons of water. In fact, for single tailed varieties, such as commons or comets, it may even become necessary to have 100 to 200 US gallons (350 to 750 L) per fish, depending on fish size. Other goldfish experts say that it is the amount of water surface area, not the water volume, that decides how many goldfish may live in a container; one square foot of water surface area for every inch of goldfish length (370 cm²/cm). For example, if you had 3 goldfish of length 4 inches each, you might need 12 square feet of water surface area. Surface area is an approximate measure of how much oxygen may be absorbed into the water from the air. If the water is being further aerated by way of water pump, filter or fountain, more goldfish may be kept in the container.

Native Environment - Contents

- Goldfish natively live in ponds, and other slow or still moving bodies of water in depths up to 20 m (65 ft). Their native climate is subtropical and they live in freshwater with a 6.0–8.0 pH, a water hardness of 5.0–19.0 dGH, and a temperature range of 40 to 106 °F (4 to 41 °C) although they will not survive long at the higher temperatures. Indeed, they are considered ill-suited even to live in a heated tropical fish tank, as they are used to the greater amount of oxygen in unheated tanks also the heat burns them.- In the wild, the diet consists of crustaceans, insects, and plant matter.While it is true that goldfish can survive in a fairly wide temperature range, the optimal range for indoor fish is 68 to 75 °F (20 to 23 °C). Pet goldfish, as with many other fish, will usually eat more food than it needs if given, which can lead to a fatal intestinal blockage. They are omnivorous and do best with a wide variety of fresh vegetables and fruit to supplement a flake or pellet diet staple.Sudden changes in water temperature can be fatal to any fish, including the goldfish. When transferring a store-bought goldfish to a pond or a tank, the temperature in the storage container should be equalized by leaving it in the destination container for at least 20 minutes before releasing the goldfish. In addition, some temperature changes might simply be too great for even the hardy goldfish to adjust to. For example, buying a goldfish in a store, where the water might be 70 °F (approximately 21 °C), and hoping to release it into your garden pond at 40 °F (4 °C) will probably result in the death of the goldfish, even if you use the slow immersion method just described. A goldfish will need a lot more time, perhaps days or weeks, to adjust to such a different temperature.Because the goldfish likes to eat live plants, keeping it with plants in an aquarium can be quite a problem. Only a few of the aquarium plant species can survive in a tank with goldfishes, for example Cryptocoryne and Anubias species, but they require special attention so that they are not uprooted.

Varieties of domesticated goldfish - Contents

Selective breeding over centuries has produced several colour variations, some of them far removed from the "golden" colour of the originally domesticated fish. There are also different body shapes, fin and eye configurations. Some extreme versions of the goldfish do need to be kept in an aquarium — they are much less hardy than varieties closer to the "wild" original, however more robust variations such as the Shubunkin are more hardy. The main varieties are:
Goldfish Scooped Up
Goldfish Scooped Up
  • Common
  • Black Moor
  • Bubble Eye
  • Celestial Eye
  • Comet
  • Fantail
  • Lionhead
  • Oranda
  • Pearlscale
  • Pompom
  • Ryukin
  • Shubunkin
  • Telescope Eye
  • Ranchu
  • Panda Moor
  • Veiltail

Chinese Goldfish Classification
In Chinese goldfish keeping, goldfish are classified into 4 main types, which are not commonly used in the west.
  • Dragon Eye - Goldfish with extended eyes, e.g. Black Moor, Bubble Eye, and Telescope Eye
  • Egg - Goldfish without a dorsal fin. e.g. Lionhead (note that a Bubble Eye without a dorsal fin belongs to this group)
  • Wen - Goldfish with dorsal fin and a fancy tail. e.g. Veiltail
  • Ce (may also be called "grass") - Goldfish without anything fancy. Which is the type that is used for Japanese carnivals, especially for "goldfish scoops".

Goldfish in ponds - Contents

Goldfish can also be kept in ponds. Common goldfish, London and Bristol shubunkins and comet can be kept in a pond all year round in Britain. Bristol shubumkin, fantail, veiltail, oranda and lionhead are only safe in the summer. Goldfish make great pondfish. They are small, inexpensive, very hardy and add much colour to the pond.Small to large ponds are fine though the depth should be at least 80 cm (30 in) to avoid freezing. During winter golfish will become slow, stop eating and often stay on the bottom. This is completly normal and in spring they will become active again. A filter is important to clear waste and keep the pond clean. Plants are not essential but can be added. Oxygenating plants are beneficial since they raise oxygen levels.Compatible fish include rudd, tench, orfe and koi but the latter will require specialised care. Ramshorn snails are helpful by eating any algae that grows in the pond.

Wild Goldfish and relationship to Crucian carp - Contents

No fancy goldfish can survive in the wild as they are handicapped (for example by fin colors).Research by Dr Yoshiichi Matsui suggests that there are subtle differences which demonstrate that while the crucian carp is the ancestor of the goldfish, they are not the same fish.

Behaviour - Contents

It is often said that goldfish have a memory span of only a few seconds, but this is not entirely true. Goldfish have what could be called a selective memory; that is to say, they have some kind of consciousness of what has happened on previous occasions, but may not be sure exactly what it was. They can learn to eat from a certain ring inside their tank, or even from their caretaker's hand, because they will remember that there is something good in that area, but might not remember what.This behaviour, or type of learning is an example of classical conditioning. If a predatory animal such as a heron is around, they will likely hide away for quite a while, but they probably do not know what it is they are hiding from; they simply know it is worth avoiding. Goldfish have a sense of time, and in captivity may be able to recognize a set feeding schedule, becoming excited before food even appears. Contrary to the notion that goldfish have poor memory, they will respond to a visit by a predator such as a raccoon, which may completely trash a small pond traumatizing the resident goldfish, which may remain extremely shy and jittery to any approach thereafter.On the television show MythBusters, Jamie Hyneman and Adam Savage explored the idea by each trying to train goldfish to navigate a maze over a 45-day period. The result was that the fish could definitely be trained to navigate the maze.
  • Mythbusters fanclub page about this episode
There is an urban legend that a pregnant goldfish is called a "twit" or "twat", but this was debunked by The Straight Dope. Also, goldfish are egglayers and do not become pregnant.

Feeding - Contents

Like most fish, goldfish are opportunistic feeders, meaning they will eat whenever food is available, whether they are hungry or not. This habit can be fatal. Their digestive tract can become so jammed with food that the intestines tear open, killing the fish. Also, an excess of food means more waste and feces, which pollute the tank. Goldfish should only be fed as much food as they can consume in 3 to 4 minutes, and no more than twice a day.A good way to tell if your goldfish is being properly fed is to look as their feces. They should be short and chunky, the same colour as the food the fish is eating. Long strings of waste that trail behind the fish as they swim could be a sign of over-feeding.Care has to be taken when choosing the right food for them, because goldfishes need less protein (which they cannot digest in excess) and more of the easy to digest carbohydrates. However, specialised food for them can be found on the market.

Breeding - Contents

Goldfish, like all cyprinids, are egglayers. They produce adhesive eggs which attach themselves to aquatic vegetation. The eggs hatch within 48-72 hours, releasing fry large enough to be described as appearing like "an eyelash with two eyeballs". Within a week or so, the fry begin to look more like a goldfish in shape, although it can be as much as a year before they take their mature goldfish colour, until then they are a metallic brown like their wild forebears. In their first weeks of existence, the fry grow remarkably fast; an adaptation borne of the high risk of getting devoured by the adult goldfish (or other fish and insects) in their environment.Goldfish can only grow to sexual maturity if given enough water and the right nutrition. However if kept well, they may breed indoors. Breeding usually happens after a significant change in temperature, often in spring. Eggs should then be separated into another tank, as the parents will likely eat any of their young that they happen upon. Dense plants such as Cabomba or Elodea or a spawning mop are used to catch the eggs.Most goldfish can and will breed if left to themselves, particularly in pond settings. Males chase the females around, bumping and nudging them in order to prompt the females to release her eggs, which the males then fertilize. Due to the strange shapes of some extreme modern bred goldfish, certain types can no longer breed among themselves. In these cases, a method of artificial breeding is used called "hand stripping". This method keeps the breed going, but can be dangerous and harmful to the fish if not done correctly.

Mosquito control - Contents

In certain parts of the world, goldfish and other carps are frequently added to stagnant bodies of water in order to reduce the mosquito populations, especially now with the arrival of West Nile Virus which relies on mosquitoes to migrate. Their introduction often had unfortunate consequences for local ecosystems, however.

Edibility and cruelty - Contents

Although edible, the fish is rarely eaten. A fad among American college students for many years was swallowing goldfish as a stunt and as an initiation process for fraternities. The first recorded instance was in 1939 at Harvard University. The practice gradually fell out of popularity over the course of several decades.In many countries, the operators of carnivals and fairs commonly give goldfish away in plastic bags as prizes for winning games. In the United Kingdom, the government proposed banning this practice as part of its Animal Welfare Bill, though early 2005 reports suggest that this idea has been dropped. However, in Rome, Italy, the city passed a law in late 2005, which banned the use of goldfish or other animals as carnival prizes. Rome has also banned the keeping of goldfish in "goldfish bowls", on the premise that it's cruel to the fish to live in such a small space.While being otherwise unkind to pretty fish may now be prohibited, killing fish (humanely) for human consumption or benign purposes (such as putting down an ill fish) is still legal in most countries (provided of course that the fish is not a protected fish caught in the wild, a fish in protected reserves or in water where the person concerned has no right to collect the fish). In the UK it is understood to be illegal to sell live fish as "feeder fish" for consumption by other fish or animals.== Common Goldfish Diseases ==Ick Ichtyopthirius is the most common of all the diseases. It is actually a parasite that attaches to the goldfish when they are stressed. When they attach themselves they are feeding off the goldfish, they look like little grains of salt. After a day or two they fall off the goldfish, landing in the gravel. They procede to lay their eggs and then the cycle starts all over again. This can be deadly if not taken care of and they will rapidly reproduce.Fin Rot Is a common problem for goldfish when they get an injury to the fins or body. Fin rot is an infection specifically a bacterial infection that occurs when a goldfish is already weak from something else. It appears as a whitish edge on the fins, then the fins rot away looking ragged and torn, sometimes fungus sets in. Most of the time this is easily cured.Fungus There are many types of fungi and can be broken down more into different categories. I'm just going to talk about the general fungus and that is normally a white cottony looking stuff that will infect an open wound. This again is a bacterial infection and needs immediate attention.Constipation This will happen to your goldfish at some time in its life. Most goldfish are compacted and this causes a problem with there ability to eat and digest things well. Foods high in fat can cause a goldfish to get stopped up just like you and I. Goldfish need green foods from time to time to help digest their foods better. Peas are the best food for them and acts as a mild laxative.Dropsy I'm not going to get into detail about this and there are people out there that can explain this better than I. Dropsy is a bacterial infection that infects the fish from the inside and you will see the scales sticking out from the goldfish's body. Normally when you see this stage of it the goldfish will most likely not live for much longer.Pop Eye The fishes eye is bulging out of the socket. This is normally the first signs of Dropsy. You can stop it with meds.Anchor Worm A white stick like worm will be sticking out of the goldfish with a red ring where it is attached. The fish normally will be rubbing against anything to get rid of it.Fish Lice This is not a pretty thing to look at, once you see it on your fish you will know what I mean. It's a greenish disk shape creature about 1/5 of an inch wide and attaches itself to the goldfish. The goldfish will be rubbing up against anything to get it off. You will also see red spots where the fish louse was. There is ways of getting rid of them but you must to it fast cause they do reproduce quickly. You can remove them from the fish manualy, then treat the tank for the ones you dont see.Swim Bladder This is not a Disease its a problem. Goldish with is problem have a floating problem either they are sinkers or floaters. The Fancy goldfish in general seem to have this problem. High levels of nitrates, not soaking there food and bad water quality can cause this problem.Body And Gill Flukes Symptoms include:excessive slime coat, isolation, clamped fins, scratching and flashing, sores and ulcers as the result of the scratching. With gill flukes, its gasping at the surface, gills being irritated and cloppy looking. Treatment: A blanket salt treatment can take care of at least 7 pathogens, but it will not affect the fluke. Commonly used treatments are pottassium permanganate (PP), Droncit, Fluketabs, Formalin and Healthguard and Quick Cure. A repeat treatment is neccessary, since the eggs or larvae can still be in the tank, even thought he first round of treatment would have killed off the mother fluke. A follow up treatment is recommended every 4 days, and just as a precaution, a third one after another 4 days. A simple dip, with great success done by JoAnn Burke, the founder of Dandy Orandas, works good as well - 1 part of hydrogen peroxide (commonly found in the stores) and 9 parts of tank water mixed together, and the fish dipped in it for no more than 10 seconds will knock both types of flukes off really good, but a treatment of the tank is still neccessary with the above mentioned medications.
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