
The common goldfish is a breed of
goldfish
The goldfish (''Carassius auratus'') is a freshwater fish in the family Cyprinidae of the order Cypriniformes. It is commonly kept as a pet in indoor aquariums, and is one of the most popular aquarium fish. Goldfish released into the w ...
and a family of
Cyprinidae
Cyprinidae is a family of freshwater fish commonly called the carp or minnow family, including the carps, the true minnows, and their relatives the barbs and barbels, among others. Cyprinidae is the largest and most diverse fish family, and t ...
in the order
cypriniformes
Cypriniformes is an order of ray-finned fish, which includes many families and genera of cyprinid ( carps and their kin) fish, such as barbs, loaches, botias, and minnows (among others). Cypriniformes is an "order-within-an-order", placed ...
. Goldfish are descendants of wild
carp
The term carp (: carp) is a generic common name for numerous species of freshwater fish from the family (biology), family Cyprinidae, a very large clade of ray-finned fish mostly native to Eurasia. While carp are prized game fish, quarries and a ...
from East Asia.
Most varieties of
fancy goldfish were derived from this simple breed. Common goldfish come in a variety of colors including red, orange, red/white, white/black, yellow/white, blue, grey/brown, olive green, yellow, white, and black, with the most common variation being orange, hence the name. The brightness, duration, and vividness of the color may be an indication of the fish's health status, but not always, as water conditions and quality of care affect the fish's appearance.
Temperament
Common goldfish are social animals that prefer living in groups. They can coexist with any
coldwater fish, as long as they're tame and sociable. With the provision of general care and attention, common goldfish can become tame. Once familiar with the face of its owner, swimming towards the fish keeper during feeding time can be observed, and hand-feeding becomes possible. Small goldfish will normally avoid any form of human contact. However, this fear ceases in a middle-sized and mature goldfish. A mature goldfish is more likely to eat directly from its owner's hand without evident hesitation. While this behavior is welcomed by goldfish owners, it may be problematic in outdoor ponds where predators may eat such friendly prey. Mature goldfish will also explore their surroundings through nibbling or grazing behavior.
If transferred into a tank with other goldfish, a common goldfish would normally try to communicate and familiarize itself with its new tank mates by rubbing up against the body of other fish. The most common introductory gesture is by swimming side by side with another goldfish with its head facing forward, or by swimming side by side with another goldfish with its head facing the opposite direction, or even by swimming above another goldfish in a perpendicular fashion.
Schooling is a common behavior when there is a new fish in the tank. After some time, this schooling behavior eventually ceases, and soon every individual fish will swim and explore the aquarium on its own. Aggressive behavior is uncommon when a new specimen is introduced into a settled school of goldfish.
Hierarchy during feeding is commonly observed, in which the larger goldfish receives most of the food. However, small goldfish may become aggressive or competitive feeders despite the presence of larger fish, which is usually considered a good sign, as a willingness to feed indicates a healthy goldfish.
Housing

It is a common practice to keep common goldfish in a small bowl, but this allows waste in the water to build up to toxic levels and does not provide enough oxygen. For each small/young goldfish, there should be a minimum of 10
US liquid gallons (38
liters; 8.3
imperial gallons) of water. A good
filter, with no heater, is recommended because these fish can get larger than .
Tank
A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and battlefield mobility provided by tracks and a powerful engine; ...
minimum recommendations range up to , although there is no maximum size. If there is concern about the fish not getting enough oxygen, particularly when it is warm, a water pump, such as a fountain pump or mini pond pump will pull the water from the bottom, expel it, and the surface action will oxygenate the tank or pond. Contrary to popular belief, air pumps and
airstones do not oxygenate directly and rely on bubbles breaking the surface to transfer oxygen to the fish's environment. Ideally, the water pump should push 10x the volume of the tank or pond plus an extra 100lph or gph. Goldfish will die without sufficient dissolved oxygen in the water. A filter that can do at least 10x filtration is best, which means that for every 10 gallons or liters of water, the filter should be able to cycle 100 gallons or liters per hour. If the oxygen in the water runs out then the fish may die or become unconscious. It is advised to move the fish to a basin of water full of freshwater.
Goldfish are curious fish that will quickly become bored without items in their tank or other fish to socialize with. If placed in a bare aquarium, goldfish will settle to the bottom and only move when fed or frightened by sudden jolts. However, if put in a tank with sufficient gravel, aquarium accessories, or plants (real or fake), they will make themselves at home.
Goldfish are not very territorial. However, if an aquarium is already too small for one goldfish, it will certainly be too small for two or more. Stress is not healthy for any goldfish. In a worst-case scenario, one or two fish will bully the rest to starvation. Cannibalism is usually rare (occurring maybe when a fish is dying or dead), but in cramped, stressful situations, goldfish may behave unpredictably. Disease is possible any time fish are stuck in small homes.
When adding goldfish to a new tank, it is important to place no more than two at a time. This allows helpful bacteria (which turn
ammonia
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...
to
nitrite
The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...
and finally to
nitrate
Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...
) to grow. If introduced in too great a number before these bacteria grow, the goldfish will die from breathing in too much of their own untreated
excrement
Feces (also known as faeces American and British English spelling differences#ae and oe, or fæces; : faex) are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the ...
. Even after the development of the biological filter, it is necessary to change about 20% of the water at least one time a week, or as necessary to prevent a buildup of harmful nitrate. The addition of live aquatic plants may reduce the number of times per month one will have to perform water changes, but only if the plants are growing (they will uptake nitrate as a source of
nitrogen
Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
). It is also recommended, if needs must, never to remove all of the water from an established tank. Never do a water change over 90%; the remaining 10% of the water will help maintain the water cycle and the remaining good bacteria will soon re-establish themselves in the tank.
A good tip when doing a water change is not to clean the filters at the same time (filters hold a good amount of helpful bacteria as well), but instead to wait two days after a water change before cleaning the filters out to keep a consistently healthy balance.
Common goldfish can be kept in
water gardens or outdoor ponds throughout the year. Outdoor ponds have similar care requirements as indoor tanks, with some notable exceptions such as amount of sunlight, natural and artificial environment pollution (i.e. dead leaves, debris,
runoff),
algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
, selection of pond mates (i.e.
algae eaters, frogs, etc.). Outdoor ponds tend to become miniature
aquatic ecosystem
An aquatic ecosystem is an ecosystem found in and around a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms—aquatic life—that are dependent on each other and on their environ ...
s, attracting various animals and plants (see
water gardens for more information). In hot climates, it is important that pond temperatures do not rise to dangerously high levels that will kill the fish.
[ In the winter, fish may become sluggish and stop feeding. This does not mean they are sick, but rather that their ]metabolism
Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...
has slowed. The pond must not freeze solid and there should be an open spot in the surface ice to allow oxygenation of the water. The ice should also not be struck, as this sends shock wave
In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...
s of sound pressure through the water, scaring the fish.
Basic common goldfish care
Mature goldfish will require a minimum tank size of 20 gallons per fish to allow ample swimming room and create a "buffer zone" that will delay the effects toxins like ammonia
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...
and nitrites from building up quickly. A larger tank also promotes healthy growth and development. Fish bowls are not suitable for goldfish as they can quickly outgrow the tank itself, which causes the fish to lose its slime coat and die from ammonia poisoning. It is important to note that not all water sources are safe for goldfish, as tap water from a city environment will usually contain chemicals like chlorine
Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...
. A water conditioner can help remove chlorine and heavy metals to make the water safe and breathable for the fish.
Goldfish have a varied diet that can include pellets, flakes, vegetables, and blood worms. Overfeeding should be avoided as it can disrupt the biological balance and increase the risk of diseases. The recommended feeding amount is what the fish can consume in 2–3 minutes, once or twice a day, depending on the size of the fish. Filtration systems help keep the tank clean and remove toxins, while also promoting good bacteria growth. It is important to choose the right filtration system to keep nitrate levels low and prevent nitrate poisoning.
Regular water changes are crucial for maintaining a clean and safe tank environment. It is recommended to change a 10–25% of the water at a time to avoid removing good bacteria from the tank. Cleaning the filter sponges and vacuuming the gravel can help remove debris and rotten food. Treated tap water at the same temperature as the tank water should be used to refill the tank. It is important to avoid using tap water to clean decorations, filters, and equipment as it can kill good bacteria.
Goldfish require adequate exposure to light to promote healthy sleeping patterns and maintain a similar environment to their natural habitat. While sunlight is beneficial, it is important to avoid exposing the fish to direct sunlight for extended periods as it can be harmful. A tank light is needed.
Breeding
Breeding common goldfish is relatively easy. In breeding conditions the male develops small white spots on his gill
A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...
covers and the female will become plump. The male chases the female until she releases her eggs, then the male releases milt to fertilize the eggs. The eggs will then stick to any available surface. It is best to remove the eggs to a separate aquarium
An aquarium (: 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. fishkeeping, Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aquati ...
, as the adults are likely to eat them. When the eggs hatch into fry, they will need to be fed very small food such as hatched brine shrimp
''Artemia'' is a genus of aquatic crustaceans also known as brine shrimp or ''Sea-Monkeys, sea monkeys''. It is the only genus in the Family (biology), family Artemiidae. The first historical record of the existence of ''Artemia'' dates back to t ...
or a ready-made fry food. As they grow bigger, they can eat finely crumbled fish food. Eventually, the pieces of fish food can get bigger.
Diseases
Common goldfish are hardy, but can contract diseases. These can be caused by poor water quality, overfeeding and overstocking. Goldfish are notoriously dirty, producing much waste, and continually stir up the substrate in their infinite search for food. In small aquarium
An aquarium (: 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. fishkeeping, Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aquati ...
s, illnesses in common goldfish can quickly become fatal and require prompt treatment. Symptoms that indicate sick fish include cuts on any of the fins, a change in scale or eye coloration, excretions from the nostrils, scales falling off or the fish frequently rising towards the water surface. Many specialty treatments are available in the market to manage specific diseases.
Diseases frequently seen in common goldfish include:
''Swim Bladder Disease'' is developed when the fish has buoyancy
Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of t ...
problems due to internal gas build-up. Swim bladder disease may be caused by insufficient fiber, poor water quality, or overfeeding. The fish "may also look physically swollen or bloated..."; it may also swim sideways or upside down. Treatment starts with testing the water to ensure cleanliness, then the goldfish should fast for three days if no improvements are made. If the fish still seems ill, then it should be fed low-protein foods and vegetables.
''Fin Rot'' is developed from bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
eating or deteriorating the fins. The disease originates from "poor water quality, overcrowding, sudden temperature changes, fin nipping, or aggressive fish"; this leads to torn and shredded fins that could deteriorate the body tissue and prevent the regrowth of their fins. Fin rot must be treated early to prevent further damage to the body tissue, so the disease does not spread. Treatments start with clean water, adding aquarium
An aquarium (: 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. fishkeeping, Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aquati ...
salt to clean the water; if that does not work, then commercial products should be used along with weekly water changes.
''White Spot Disease'' is caused by the protozoa
Protozoa (: protozoan or protozoon; alternative plural: protozoans) are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. Historically ...
n parasite Ichthyophthirius multifiliis, colloquially known as "ich." The parasite
Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...
embeds itself into the host's skin to feed on its tissue and blood. This causes the epidermal cell
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the amount of water relea ...
s to proliferate and form pinhead-sized white spots that appear on the fins and body. It is usually introduced into the pond or aquarium on infected fish or contaminated equipment. Once considered a tropical fish disease, it is now a common goldfish illness. Fish may not always display the characteristic white spots. Ich sometimes limits infection to the gills and the only sign that a fish is infected is an increase in breathing rate, lethargy, and clamped fins. If left untreated, in a small volume of water such as an aquarium the infected fish can quickly succumb to the rapidly multiplying parasites. The parasite can only be killed once it has left the host. To speed up the parasite's five-stage life cycle, increase the water temperature to between 27 and 30oC (81–86oF). Water quality parameters - ammonia, nitrite, nitrate and pH - need to be optimal. Non-iodized
Iodised salt (American and British English spelling differences#-ise, -ize (-isation, -ization), also spelled iodized salt) is Salt#Edible salt, table salt mixed with a minute amount of various iodine salts. The ingestion of iodine prevents iod ...
plain cooking salt or aquarium salt is added to the water at a concentration of 0.3% or 3 teaspoons per gallon. The first teaspoon is added immediately, the second after 12 hours, and the last 12 hours later. Within a few days, the cysts should start disappearing. The fish is left in the salt bath for a few more days to allow its skin to heal while the water temperature is slowly decreased.
''Fungal Infection'' is the growth of fungus
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
, which could lead to parasitic infections, ulcer
An ulcer is a discontinuity or break in a bodily membrane that impedes normal function of the affected organ. According to Robbins's pathology, "ulcer is the breach of the continuity of skin, epithelium or mucous membrane caused by sloughin ...
s, or open wounds. The fungus symptoms could also lead to a secondary fungal infection. There are "cotton-like growths along the body and fins", which is caused by dirty water. Treatments start by moving the goldfish to a hospital tank and then clearing the environment with Methylene blue
Methylthioninium chloride, commonly called methylene blue, is a salt used as a dye and as a medication. As a medication, it is mainly used to treat methemoglobinemia. It has previously been used for treating cyanide poisoning and urinary trac ...
. If the condition is serious, however, the goldfish can just have a cleaner tank and the fungal infection should clear up over time.
''Ammonia poisoning'' is caused by high levels of ammonia
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...
in the tank. Add ammonia reduction chemicals to the tank, or for an emergency release of ammonia, change the water 25 percent daily for one week until the symptoms decrease. Ammonia reduction chemicals must not be added as soon as the ammonia levels drop, as ammonia removers can starve the biological filter and cause the cycling process to start over.
'' Fish lice'' is a parasite. Fish lice move on the body of fish. The only visible parasites, they look like clear white splodges. These lice can have nasty health side effects to the fish. Try to avoid removing the lice manually; use anti-parasite medicine.
''Bacterial diseases'' can be deadly, but treatments are available at local fish stores.
Lifespan
Goldfish can live for long periods of time if they are fed a varied diet and housed in proper water conditions. The average lifespan of a goldfish is ten to fifteen years. The longest-lived goldfish on record lived to age 43. The oldest living goldfish was Tish, won by a UK family at a funfair. Tish was recognized into the Guinness Book of World Records
''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a British reference book published annually, listi ...
as the longest living goldfish. Improper care or life in a bowl greatly reduces the typical lifespan of a goldfish.
As feeder fish
Common goldfish are often used as live prey for freshwater turtles, notably red-eared slider
The red-eared slider or red-eared terrapin (''Trachemys scripta elegans'') is a subspecies of the pond slider (''Trachemys scripta''), a semiaquatic turtle belonging to the Family (biology), family Emydidae. Native to the southern United States ...
s, and carnivorous fish such as oscars
The Academy Awards, commonly known as the Oscars, are awards for artistic and technical merit in film. They are presented annually by the Academy of Motion Picture Arts and Sciences (AMPAS) in the United States in recognition of excellence i ...
. When fed exclusively, feeder goldfish are a poor source of nutrients. They can introduce unwanted pathogens into the home aquarium, as they are usually given minimal care before being sold.
Confusions with comet goldfish
The common goldfish are often confused with comet goldfish, a distinct breed. The two breeds are often mixed together at many pet stores and aquarium stores. The breeds differ in the relative size of the body and fins. The comet goldfish has longer fins but a shorter and slender body size, and thus resembles tracing comet
A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...
s. The most recognizable difference is their tails. Usually, a common goldfish has a short stubby tail, and the comet's tail extends over half of the body length. The common goldfish usually resembles the wild carp more closely than the comet goldfish. Comets are sometimes said to display a wider variety of colors, but common goldfish also display many of the same types of colors, including red/white, blue, red, orange, yellow, and other two-toned colors like black/orange.
References
{{Goldfish breeds