Goldfish are fun to watch! Just look at all the different colors of these beautiful fish!

The Common Goldfish Carassius gibelio (previously Carassius auratus auratus) are hardy fish that are well known by all aquarists. They are colorful, inexpensive, and readily available. These fish are a favorite pet for a multitude of keepers because they can be quite personable and are delightful to watch.

The Common Goldfish is a small member of the Cyprinidae family of carp fish. The popular Koi fish, which is commonly kept in ponds, is also a member of the carp family. The C. gibelio was originally a silver or gray color, but early in the Jin Dynasty, somewhere between the years 265 – 420, breeders noticed a natural genetic mutation producing a yellowish-orange color.

It became common practice to breed this pretty golden fish. Over time, a large variety of breeds of varying shapes and sizes have been developed. Other natural mutations are red and yellow. Today, Common Goldfish are available in various solid colors and combinations of white, yellow, orange, red, brown, and black.

These are one of the hardiest of the goldfish varieties. They are known as a choice beginner fish for new aquarists because they are one of the easiest fish to keep. They can handle a variety of aquarium conditions and are not picky about food, readily eating what is offered. Selecting them is also fun because they come in such a diverse mix of colors.

Most freshwater aquarium fish are tropical, but goldfish are an exception. These are coldwater fish, preferring a tank kept between between 65 – 72° F (18°- 22° C). Still, these durable fellows are very versatile and can tolerate everything from tropical temperatures all the way down to a few degrees above freezing, as long as the cooling drops only a few degrees a day. They can be maintained without a heater or a filter, as long as the water is changed out frequently.

These are active fish and they can swim fairly fast, but they are also very social. They thrive well in a community. Along with the other elongated goldfish, such as the Comet Goldfish and the Shubunkin Goldfish, they make good pond fish. They are fast and get along well with Koi, but they readily spawn and can quickly overpopulate your pond.

If they are kept in a community with other freshwater fish, the aquarium needs to be designed for the needs of the other fish. Not only will it need a heater, but it will also need a good filtration system. Goldfish place a much heavier bioload on the aquarium than most other tropical fish, so more frequent water changes are necessary to keep the water quality up.

Scientific Classification

Species:auratus auratus

Common Goldfish – Quick Aquarium Care

Aquarist Experience Level:Beginner
Aquarium Hardiness:Very hardy
Minimum Tank Size:15 gal (57 L)
Size of fish – inches4.0 inches (10.16 cm)
Temperature:65.0 to 72.0° F (18.3 to 22.2&deg C)

Habitat: Distribution / Background

The goldfish of today are descendants of a species of wild carp known as the Prussian Carp, Silver Prussian carp, or Gibel Carp Carassius gibelio (syn: Carassius auratus gibelio), which was described by Bloch in 1782. These wild carp originated in Asia; Central Asia (Siberia). They inhabit the slow moving and stagnant waters of rivers, lakes, ponds, and ditches feeding on plants, detritus, small crustaceans, and insects.

For many years, it was believed that goldfish had originated from the Crucian Carp Carassius carassius described by Linnaeus in 1758. This fish has a wide range across the waters of the European continent, running west to east from England to Russia, north to Scandinavian countries in the Arctic Circle and as far south as the central France and the Black Sea. However, recent genetic research points to C. gibelio as a more likely ancestor.

Goldfish were originally developed in China. This species was normally a silver or gray color, but early in the Jin Dynasty, somewhere between the years 265 – 420, it was noted that there was a natural genetic mutation producing a yellowish orange color. It became common practice to breed this pretty golden fish for ornamental garden ponds.

By the 1500s, goldfish were traded to Japan, to Europe in the 1600s, and to America by the 1800s. The majority of the fancy goldfish were being developed by Asian breeders. The results of this centuries-long endeavor is the wonderful goldfish colors and forms we see today.

Besides gold, other natural color mutations are red and yellow, and now there are also various solid colors and combinations of white, yellow, orange, red, brown, and black. Today, domesticated goldfish are distributed world-wide and there are more than 125 captive-bred varieties.

  • Scientific Name: Carassius auratus auratus
  • Social Grouping: Groups – Can be kept singly or in groups.
  • IUCN Red List: NE – Not Evaluated or not listed


The Common Goldfish is an elongated, flat-bodied variety of goldfish. The head is wide but short and its body tapers smoothly from its back and belly to the base of its caudal fin (tail fin). The caudal fin is forked. Its fins generally stand fully erect and the edge of the dorsal fin is slightly concave.

The average goldfish lifespan is 10 – 15 years, though living 20 years or more is not uncommon in well-maintained goldfish aquariums and ponds.

The environment the Common Goldfish is kept in is a determining factor on whether your pet will grow to its full potential size or remain somewhat smaller. In an average 15 gallon tank, if well cared for and not crowded, they can grow up to about 4 inches (10 cm). In a larger, uncrowded tank, they can grow generally reach about 7 or 8 inches (17.78 – 20.32 cm). If kept in a spacious pond, they can reach over 12 inches (30+ cm) with some hobbyists reporting their goldfish reaching up to a whopping 18″ (45+ cm)!

There are various solid colors and combinations of white, yellow, orange, red, brown, and black. The most distinguished specimen is a bright orange metallic color.

The Common Goldfish is very similar to, and sometimes confused with, the Comet Goldfish. The Comet is a further development of the Common Goldfish. Both these fish have an almost identical body shape but the fins on the Comet are much longer, especially the caudal (tail) fin, which is more deeply forked. Also, the Comet is generally a reddish-orange while the Common Goldfish is more orangish. The adult size of the Comet Goldfish is smaller, too. On both these fish, the caudal (tail) fin is held fully erect.

Also, in the standard orange color the Comet is generally a more reddish orange while the Common Goldfish is more orangish. The adult size of the Comet Goldfish is smaller too. On both these fish the caudal (tail) fin is held fully erect.

Another goldfish that is almost identical to the Common Goldfish is the ‘London’ type of Shubunkin Goldfish. Both these fish have virtually the same body and fin shapes, but the London type Shubunkin Goldfish has a totally different body color. While a good specimen of the Common Goldfish will have a bright orange metallic color, this London type Shubunkin goldfish can be speckled or have a variegated color pattern.

  • Size of fish – inches: 4.0 inches (10.16 cm) – Average size is 4″ (10. cm) but can reach about 7 or 8 inches (18 – 20 cm) if not crowded. If kept in a spacious pond, they can reach over 12 inches (30+ cm). Some hobbyists report their Common Goldfish reaching up to a whopping 18″ (45+ cm).
  • Lifespan: 15 years – The average goldfish lifespan is 10 – 15 years, but they have been known to live 20 years or more when well maintained.

Fish Keeping Difficulty

Common Goldfish are some of the hardier species of goldfish. They are very undemanding of water quality and temperature. They can do well in a goldfish aquarium or even a pond as long as the environment is safe and their tankmates are not competitive.

Many people will keep goldfish in an aquarium with no heater or filtration, but for the best success, provide them with the same filtration, especially biological filtration, that other aquarium residents enjoy.

  • Aquarium Hardiness: Very Hardy
  • Aquarist Experience Level: Beginner

Foods and Feeding

Since they are omnivorous, the Common Goldfish will generally eat all kinds of fresh, frozen, and flake foods. To keep a good balance give them a high quality flake food everyday. To care for your goldfish, feed brine shrimp (either live or frozen), blood worms, Daphnia, or tubifex worms as a treat. It is usually better to feed freeze-dried foods as opposed to live foods to avoid parasites and bacterial infections that could be present in live foods.

  • Diet Type: Omnivore
  • Flake Food: Yes
  • Tablet / Pellet: Yes
  • Live foods (fishes, shrimps, worms): Some of Diet
  • Vegetable Food: Some of Diet
  • Meaty Food: Some of Diet
  • Feeding Frequency: Several feedings per day

Aquarium Care

These goldfish are hardy and easy to keep in a well-maintained tank. Minimum tank size is 15 gallons, but make sure water changes are frequent in such as small tank. Regular weekly water changes of 1/4 to 1/3 are strongly recommended to keep these fish healthy. Snails can be added as they reduce the algae in the tank, helping to keep it clean.

  • Water Changes: Weekly – Goldfish produce more waste than most other freshwater fish and benefit greatly from more frequent water changes.

Aquarium Setup

Setting up a goldfish aquarium in a manner that will keep your fish happy and healthy is the first step to success. The shape and size of the aquarium is important and depends upon the number of goldfish you are going to keep. These fish need a lot of oxygen and produce a lot of waste. Good filtration, especially biological filtration, is very helpful in maintaining the water quality of the aquarium. A filtration system will remove much of the detritus, excess foods, and waste, which keeps the tank clean and maintains the general health of the goldfish.

  • Tank parameters to consider when choosing a goldfish aquarium:
    • Tank size
      Fifteen gallons is the absolute minimum required to house a Common Goldfish. It’s best to start with a 20 – 30 gallon tank for your first goldfish and then increase the size of the tank by 10 gallons for each additional goldfish. Providing a large amount of water per fish will help dilute the amount of waste and reduce the number of water changes needed.
    • Tank Shape
      Always provide the maximum amount of surface area. A large surface area minimizes the possibility that the goldfish will suffer from an oxygen shortage. Surface area is determined by the shape of the tank. For example an elongated tank offers more surface area (and oxygen) than a tall tank. Oval or round tanks that are wide in the middle and narrower toward the top might be filled less than full to maximize the surface area.
    • Number of fish
      For juveniles a general rule of thumb is 1 inch of fish (2.54 cm) per 1 gallon of water. However, this rule only applies to young fish. Larger gold fish consume much more oxygen than young fish so maintaining this formula for growing fish will stunt them and could contribute to disease and even death.
    • Fish size and growth
      To allow for proper growth, either buy fewer fish than the maximum number or be prepared to get a larger tank. To prevent stunted growth and other health problems, don’t overstock the aquarium.

Goldfish are a cold water fish and will do best at temperatures between 65 – 72° F (18°- 22° C). The Common Goldfish are one of the most hardy varieties of goldfish and can tolerate temperatures a few degrees above freezing, as long as the cooling drops only a few degrees a day. A quick temperature drop can kill them, so if you live in a very cold climate, a heater is advisable.

Provide a gravel substrate to help create a natural and comfortable environment for your fish. You can add some decor, but make sure that all ornamentation is smooth with no protruding points or sharp edges. Smooth rocks or driftwood should be used sparingly if at all. Aquarium  plants are the best choice of aquarium decor for goldfish, but unfortunately, these fish are diggers and my uproot live plants. Artificial plants make a good substitute, and silk plants are safer than plastic ones.

Most aquariums come with a cover that includes lighting. A cover for the tank is desirable as it reduces evaporation, and though they are not prone to jumping, on occasion some goldfish will jump out. Lighting is not essential for goldfish, but does make the aquarium a nice showpiece and will help if you have live plants.

  • Minimum Tank Size: 15 gal (57 L) – 15 gallons is the absolute minimum for this variety of Goldfish, and 25 gallons is really best. This fish can grow to over a foot in length, keeping it in a small tank will stunt its growth and cause irreversible damage.
  • Suitable for Nano Tank: Sometimes – A Nano tank is fine as long as it is 15 gallons or more. A larger tank will be needed for a community.
  • Substrate Type: Any – Any medium-sized gravel works best.
  • Lighting Needs: Moderate – normal lighting
  • Temperature: 65.0 to 72.0° F (18.3 to 22.2&deg C) – Goldfish can tolerate colder temperatures, but this is the optimum range for activity and longevity in Goldfish.
  • Breeding Temperature: – In the wild, goldfish spawn in the spring when water temperatures reach about 68° F (20° C).
  • Range ph: 6.0-8.0
  • Hardness Range: 5 – 19 dGH
  • Brackish: Sometimes – Goldfish are freshwater fish, but they have some tolerance for slightly brackish water. Any salinity for must be kept low, below 10%, a specific gravity of less than 1.002.
  • Water Movement: Moderate
  • Water Region: All – These fish will swim in all areas of the aquarium.

Social Behaviors

Goldfish are very social animals and thrive in a community. Not only are they a great community fish, but they are great scavengers as well. It is really not necessary to add other scavengers or other bottom feeders to the aquarium when you have goldfish.

Most fancy goldfish will thrive in both freshwater and tropical aquariums as long as there are no aggressive or territorial fish in the tank. Some good tankmates for fancy goldfish are the Chinese Blue Bitterling and the Northern Redbelly Dace.

Common Goldfish can be kept with other varieties of elongated goldfish, such as the Comet Goldfish and the Shubunkin, and they also do fine with Koi.

  • Venomous: No
  • Temperament: Peaceful – This fish is active and friendly.
  • Compatible with:
    • Same species – conspecifics: Yes
    • Peaceful fish (): Safe
    • Semi-Aggressive (): Threat
    • Aggressive (): Threat
    • Shrimps, Crabs, Snails: Safe – not aggressive
    • Plants: Threat – Goldfish produce more waste than most other freshwater fish and benefit greatly from more frequent water changes.

Sexual differences

During the breeding season the male has white prickles, called breeding tubercles, on its gill covers and head. Seen from above a female will have a fatter appearance when she is carrying eggs. It is impossible to sex Goldfish when they are young and not in breeding season, but generally the male is smaller and more slender than the female.

Breeding / Reproduction

Common Goldfish are egg layers that spawn readily in the right conditions. They can be bred in groups as small as five individuals, but they are very social animals and likely to breed in larger groups as well. The only time Goldfish will spawn in the wild is when spring arrives. To spawn them in the aquarium, you will need to mimic the conditions found in nature.

Provide an aquarium that is at least 20 gallons and make sure the fish are healthy and disease free. Some breeders suggest you treat them for parasites. Many breeders will also separate the males and females for a few weeks prior to breeding to help increase their interest in spawning. Introduce the fish into the breeding tank at the same time. The tank will need a lush environment with solid surfaces for the spawning process and for the eggs to adhere to. Bushy, oxygenating plants, such as Anacharis, work well for this, though artificial plants or fibrous spawning mops can also be used.

To induce spawning, the temperature can be slowly dropped to around 60° F (11° C) and then slowly warmed at a rate of 3° F (2° C) per day until they spawn. Spawning generally begins when the temperatures are between 68° and 74° F (20°-23° C). Feeding lots of high protein food such live brine shrimp and worms during this time will also induce spawning. Feed small amounts three times a day, but don’t overfeed. Uneaten scraps will sink to the bottom and foul the water. Maintain the breeding tank with partial water changes of up to about 20% per day.

Before spawning, as the temperature increases, the male will chase the female around the aquarium in a non-aggressive way. This can go on for several days, and the fish will intensify in color. During the spawn, the fish will gyrate from side to side, and the male will push the female against the plants. This stimulates the female to drop tiny eggs which the male will then fertilize. The eggs will adhere by sticky threads to the plants or spawn mop. Spawning can last two or three hours and can produce up to 10,000 eggs.

At this point, the parents will start to eat as many eggs as they can find. For this reason, it is best to remove the parents after spawning is complete. The fertilized eggs will hatch in 4 to 7 days, depending on the temperature. You can feed the newly hatched goldfish specialty fry foods until they become big enough to eat flake or brine shrimp, or you can offer the same food as you feed the parents as long as it is crushed very small. At first, the fry are a dark brown or black color in order to better hide and not be eaten by larger fish. They gain their adult color after several months and can be put in with larger fish once they reach about 1 inch long. See Breeding Freshwater Fish – Goldfish for more information on breeding Goldfish.

  • Ease of Breeding: Easy

Fish Diseases

In properly maintained goldfish aquariums or ponds, goldfish illness is largely preventable. Even so, goldfish illnesses can occur, and if left untreated, may prove fatal. Goldfish are hardy, though, and if treated in a timely manner, most will make a full recovery.

When treating individuals, it is usually best to move the afflicted fish into a separate tank with no gravel or plants and do regular partial water changes. However, if the disease is apparent throughout the main tank, it may be best to do the treatments there. Whether treating in a hospital tank or your main tank, read and follow the manufacturer’s instructions for any medication. Some medications can adversely affect the water quality by destroying beneficial bacteria. You may also need to remove the carbon from the filtration system, as carbon will absorb many medications, making the treatment ineffective.

Goldfish diseases are mostly the same as those that afflict other freshwater fish, and the symptoms and treatment of goldfish are also similar. The main types of fish diseases include bacterial infections, fungal infections, parasites, and protozoa. There are also other ailments caused by injury, poor nutrition, or bad water conditions.

One of the more common problems is Ich, which is a protozoan disease. Ich is easy to identify because your fish looks like it is sprinkled with salt. Though Ich is easily treated, like other protozoan diseases, it can be fatal if not caught quickly. Some other protozoan diseases are Costia, which causes a cloudiness of the skin, and Chilodonella, which will cause a blue-white cloudiness on the skin.

External parasites are fairly common, too, but pretty easy to treat and usually not fatal when treated. These include flukes, which are flatworms about 1 mm long with hooks around their mouths. They infest the gills or body of the fish. Another type of parasite is fish lice (Argulus), flattened, mite-like crustaceans about 5 mm long that attach themselves to the body of the goldfish. Lastly, anchor worms look like threads coming out of the fish.

Some bacterial infections include Dropsy, an infection in the kidneys that can be fatal if not treated quickly. Fish Tuberculosis is indicated by the fish becoming emaciated (having a hollow belly). For this illness, there is no absolute treatment, and it can be fatal. Tail/Fin Rot may also be bacterial, though the reduced tail or fins can be caused by a number of factors as well. There is also fungus, a fungal infection, and Black Spot or Black Ich, which is a parasitic infection.

Swim Bladder Disease is an ailment indicated by fish swimming in abnormal patterns and having difficulty maintaining their balance. This can be caused by a number of things: constipation, poor nutrition, a physical deformity, or a parasitic infection. Feeding frozen peas (defrosted) has been noted to help alleviate the symptoms and correct the problem in some cases.

Other miscellaneous ailments include Cloudy Eye, which can be caused by a variety of things ranging from poor nutrition, bad water quality, and rough handling. It can also be the result of other illnesses, such as bacterial infections. Constipation is indicated by a loss of appetite and swelling of the body, and the cause is almost always diet. Then there are wounds and ulcers. Wounds can become infected, creating ulcers. Wounds can develop either bacterial or fungal infections, or both, and must be treated. There are treatments for each of these diseases individually and treatments that handle both. For more in-depth information about goldfish diseases and illnesses, see Goldfish Care; Fancy Goldfish and Goldfish Diseases.


The Common Goldfish is inexpensive and readily available in fish stores and online.



Featured Image Credit: JuanCarlosPalauDiaz, Shutterstock