Carassius auratus – Goldfish

(Linnaeus, 1758)
Pronounced: car-ace-EE-uss oar-ART-uss

Carassius auratus – Goldfish

Carassius auratus – Goldfish Quick Facts:

  • Availability: *****
  • Hardiness: ****
  • Overall appeal: ****

Common name

known collectively as Goldfish. Individual varieties also have common names, including Oranda, Comet, Pearlscale, Ryukin and Celestial Eye. These will be dealt with individually in separate Fact Sheets.

Adult size

The torpedo-shaped Goldfish (eg. Comets and Shubunkins) grow over 30 centimetres in length.
The Fancy Goldfish tend to stay smaller, the largest of which may reach 20 centimetres.


Adult males develop white pimples onaround their head during the spawning season. Females are plumper than males. Both sexes are colourful.

Carassius auratus – Goldfish
Carassius auratus – Goldfish


Vegetarian/Omnivore – all varieties of Carassius auratus are mostly vegetarian, although they will accept any food. To keep them healthy they should be fed a diet high in vegetable material. Commercial goldfish foods contain the right balance of vegetable and protein.

Swimming level

mainly inhabits the bottom level of the aquarium, but some will come to the surface when fed.

Recommended for

outdoor ponds (Torpedo-shaped fish); large unheated tanks; large filtered bowls as appropriate to size; beginners to experienced fishkeepers.

  • The genus name Carassius is a Latinisation of karass or karausche the European crucian carp.
  • The specific name auratus comes from Latin word auratus meaning gold.
  • The Goldfish was first described in 1758 by Linnaeus as Cyprinus auratus. Carassius auratus became the valid scientific name in 1949.
  • The common Carassius auratus has been kept in captivity longer than any other fish.
  • The earliest goldfish were colour mutations of the Gibel Carp. They caught the eye of the Chinese as early as 265 AD.
  • During the Tang dynasty (618-907 AD) Buddhist monks began to keep golden Gibel Carp in ponds.
  • In the Song dynasty (1127-1279 AD) enthusiasm on the part of the royal family led to extensive breeding and ultimately domestication of what is now the goldfish.
  • Carassius auratus were introduced to Japan and Europe in the 1600’s and to the US in the late 1800’s.
  • Conservative estimates place the numbers of goldfish varieties at 150.
  • Japanese breeders learned the art from the Chinese and carried their interest in the species to the point of holding annual goldfish exhibits throughout the country.
  • Carassius auratus are reported to have been introduced into England in 1691 and into France in the middle of the 18th century, when specimens were received as gifts by the Marquise de Pompadour, mistress of King Louis XV.
  • Today they are produced in many countries on a sizable commercial scale. One goldfish hatchery in Maryland, occupies 40 hectares and has an annual production of 5 million fish.
  • Goldfish are the most common pet found in households today!
  • The world record for the oldest Carassius auratus is 41 years.
  • It has been estimated that there are over 125 varieties of Goldfish.


  • Descriptions of some of the numerous varieties of Carassius auratus are detailed in separate Fact Sheets.
  • There are basically two distinct body types – Torpedo-shaped and Egg-shaped. The Egg-shaped Goldfish are also known as Fancy Goldfish.
  • Within the Egg-shaped varieties there are fish with or without dorsal fins, single and double-tailed, fish with unusual eyes and head growths, as well as a variety of colours and patterns.
  • Within the Torpedo-shaped varieties the variation is more limited – single or double tailed and colour.

Similar species…

Koi Carp (Carassius carpio) look similar to the comet and shubunkin-type Goldfish. However, Koi have barbels on each side of their mouth, that Carassius auratus lack.

Taxonomy and systematics….


  • Kingdom: Animalia
    • Phylum: Chordata
      • Class: Actinopterygii (Ray-finned Fish)
        • Order: Cypriniformes (Carps)
          • Family: Cyprinidae (Minnows or Carps)
            • Genus: Carassius
              • Species: auratus

Geographical variants….

Not applicable, as many man-bred forms exist.

In the wild, goldfish can be found in slow-moving, freshwater bodies of water. As with their close relative the carp, they thrive in slightly sludgy water. None of the Carassius auratus varieties found in aquariums occur naturally in the wild. They are all specifically bred for a particular characteristic – colour, fin or body shape, etc. The closest in shape to the wild Goldfish is the Comet, although the wild form is a slightly stockier fish with shorter fins.

Information relating to tank size is indicative and depends on factors including the type and size of fish kept with the species being discussed. It is intended to be used as a rough guide only to give some idea of the space requirements for the fish.


  • Goldfish thrive in large tanks or outdoor pools supplied with clean, well-aerated water.
  • Fancy Goldfish are not suitable for outdoor ponds.
  • Comets (right) and Shubunkins must be kept in tanks with lids as they will jump.
  • Smaller tanks may be used for juvenile fish initially.
  • When you begin your aquarium, you need to keep in mind that it is a home for your fish. Carassius auratus require more room than other varieties of fish. As a general guide: 1 fish per 50 litres of water.


  • Use a fine rounded gravel substrate and if using rocks and wood make sure there are no sharp edges that the fish could damage itself on.
  • All of the swimming and vision-impaired breeds do best with no decorations at all, except for gravel and live (or plastic) plants. Rocks and driftwood and ceramic castles are merely obstacles to most of these fish.
  • Real plants can be used, however, as all Goldfish are vegetarians they will eat soft plants. Elodea is the ideal plant to use with Carassius auratus as it is a coldwater plant, quick growing and, although the Goldfish will eat it, it can be easily replaced.
Carassius auratus – Goldfish
Carassius auratus – Goldfish

Maintenance and Disease….

  • Goldfish are extremely messy fish and good filtration is essential to remove the waste the produce. Small, weekly water changes, about 10-20 percent, shoud be undertaken to keep the water clear.
  • All of the single tail varieties are quite hardy and are the most forgiving of imperfect conditions.
  • Goldfish are not tropical fish; therefore, they do not require a heater in the tank. Typically, Carassius auratus will survive in water temperatures ranging from freezing to about 28oC. They do much better in cooler temperatures.
  • Fancy Goldfish should be kept in water no cooler than room temperature. They aren’t really suited to outdoor ponds (although many will do well in large containers in sheltered areas (such as a balcony) away from predation and weather extremes.
  • They should not be overfed.
  • Some diseases seem to affect Carassius auratus more than other fish – watch particularly for Dropsy, Fish Lice and Fin or Tail Rot (in longtailed varieties). Some of the Fancy Goldfish, such as Orandas and Lionheads can develop fungal growths in their head caps if the water quality is poor.
  • Too much ammonia in the water shows as blood lines in the ribs of the fins and tail.
  • Many Carassius auratus diseases can be avoided by just meeting the minimum acceptable levels of care and hygiene.
  • Most Goldfish are pretty hardy if their needs are met.
  • The addition of aquarium salt to the water is beneficial for Carassius auratus.
  • Water parameters:
    • pH: slightly acid to slightly alkaline (6.5-7.5: optimum 7.0)
    • Hardness: soft (5-30dH)
    • Temperature: 17-28oC.


  • Goldfish should preferrably be kept with Goldfish.
  • In the wild they will school to a certain extent. In aquariums, however, they can be kept seperately or in a group. Carassius auratus are quite intelligent and will recognise the person who feeds them.
  • Goldfish are not particularly aggressive, so combining sizes is not often a problem. However, Carassius auratus with different body shapes should not be kept together. For instance, a slow, heavy-bodied Oranda should not be kept in the same tank with a fast, slightly more aggresive variety such as a Comet.
  • Algae eaters such as the Chinese Algae-eater, are not recommended for Fancy Goldfish, as they are very quick, grow large and, if their is not enough algae in the tank, will suck the slime coating from the slow-moving Fancy Goldfish.

The fish listed below are indicative of the species that can be kept with this fish. Other fish may also be suitable – please ask us which other fish are compatible.


Goldfish of similar body shape are suitable to keep together
Chinese Algae-eater(Gyrinocheilus aymonieri)*
White Cloud Mountain Minnow (Tanichthys albonubes)
Rosy Barb (Barbus conchonius)*
Bitterling (Rhodeus ocellatus)*

South America

Bristlenose Catfish (Ancistrus sp)
Pleco (Glyptoperichthys multiradiatus)

Central/North America

Swordtail (Xiphophorus hellerii)
Shiner (Notropis lutrensis)*

* Should not be kept with the less robust or slower Fancy Goldfish, such as Bubble-eyes, Ranchus and Celestial-eyes.


  • Males will chase females for several days before spawning occurs.
  • Females can produce several thousand eggs per spawning period up to several times within a few months. The males release milt into the water, which will turn the water a milky-white (right).
  • During the spawning season the male will have tubercles (small white dots, not to be confused with the disease White Spot) on their head, pectoral fins and gill covers.
  • Goldfish eggs hatch in about 4-5 days at between 18-20oC.
  • The parents are voracious egg eaters and must be removed immediately after spawning.

Because there are many different Carassius auratus varieties, each with different characteristics and requirements, separate Fact Sheets have been developed to provide more information specific to that particular type.

Goldfish today vary enormously from the original Common Goldfish. They come in many different colours and patterns – yellow, orange, red, gold, white, blue and black. Some have calico patterns, yet others have long, veil-like fins and others have double fins. Some varieites have no dorsal fin, others have coloured fleshy growths on the head; strange eyes; egg-shaped bodied or high backs. Many varieites have one or more different traits.

The Fact Sheets are divided broadly into information on:

  • Single tail (Torpedo-shaped) Goldfish
    • Comet and Shubunkin
  • Double tail (Torpedo-shaped) Goldish
    • Wakin
  • Double tail Fancy Goldfish
    • Fantail, Black Moor, Telescope, Ryukin
  • Other Double tail Fancy Goldfish
    • Oranda, Pearscale
  • Fancy Goldfish with no dorsal fin
    • Ranchu, Lionhead
  • Fancy Goldfish with different eyes
    • Bubble-eye, Celestial-eye

What to Look for in a Fancy Goldfish

  • All Fancy Goldfish – Deep, rich colouring; Smooth, undamaged fins without blood spots, frayed edges or major tears.
  • Ryukins – The higher the back the better; Head should be narrow and come to a point.
  • Ranchus and other dorsal fin-less varieties – Smooth curved back; No sign of vestigal dorsal fins
  • Orandas – Head growth should cover as much of the head as possible without covering the eyes. It should sit on top of the head like a hat; no fungus on head growth.
  • Pearlscale – Every scale should be pearled; Back should be completely pearled.
  • Bubble-eyes – Both eye sacs inflated and even in size.
  • Telescopes-eye – Eyes the same size.

These Goldfish are also referred to as Egg-shaped Goldfish. They have the typically rounded body shape of other Fancy Goldfish, but have no dorsal fin. The two most common varieties are the Ranchu and the Lionhead. These fish are similar, with a headgrowth, short double caudal fins, and smooth back contours without evidence of the missing dorsal fin.

The Ranchu (right) has been known in Japan since the 1700s and the first competitive Ranchu exhibition was in 1885. The Lionhead is about 300 years older and it is thought that the Ranchu was developed from the Lionhead.

The Lionhead gets its name from the massive headgrowth, which grows beyond the top-of-the-head cap of the Oranda, becoming a «mane» all around the head and gills. In addition, the dorsal fin is completely absent, and the other fins are greatly reduced in size. This produces a softball-with-fins appearance, and many large lionheads are very ungainly when swimming.

These fish should never be kept with more agile breeds, who will get all the food and bully the awkward Lionheads. This in another dorsal less breed that has the same general characteristics as the Ranchu. this Chinese breed has much larger head growth and this breed has the largest head growth of any breed. A double tail propels the short boxy body. View this tail from above and the tail looks like butterfly wings, which is very attractive. the back outline is straighter than found in the Ranchu, but it still has a gentle, even curve, which is carried right to the caudal peduncle.

Scroll al inicio