Carassius auratus: Goldfish Species Facts, Size and ID

Carassius auratus is the scientific name of the goldfish, a freshwater fish in the carp family Cyprinidae (FishBase) that comes from East Asia. FishBase explains the name: Carassius comes from karass, an old Eurasian name for these fish, and auratus means gilded.

What about Carassius auratus auratus? You will see that three-part name in older books and shop labels. Wikipedia explains that the goldfish was long treated as a subspecies of the Prussian carp (Carassius gibelio) or the crucian carp (Carassius carassius), but modern genetic sequencing indicates that goldfish are domesticated varieties of C. auratus, native to southern China. Today Carassius auratus is the usual name.

The gold colour itself is a mutation. Wikipedia says a natural mutation produced gold, really yellowish orange, instead of the normal silver colouring during the Tang dynasty (618-907), and people then kept and bred those fish.

A goldfish is a member of the carp family, but it is not the common carp. It shares the genus Carassius with the crucian carp and the Prussian carp, while the common carp belongs to a different genus. The quickest field check is the mouth: goldfish have no barbels (USGS), while common carp have barbels at the corners of the mouth; see our common carp page.

The line can blur in the wild. USGS notes that goldfish commonly hybridise with common carp and with Prussian carp, producing fish that look intermediate between the parents. If a big orange "goldfish" has short barbels, a hybrid is the likely answer.

The wild colour of the species is silver, the colour the gold mutation replaced (Wikipedia), and released goldfish in lakes are not always orange, so use body features rather than colour (USGS unless noted):

• Long dorsal fin with 15 to 21 rays
• A hard, serrated spine at the front of both the dorsal and anal fins; USGS says the serration separates goldfish from other Asian carp-family fish with smooth spines
• No barbels on the mouth
• 25 to 31 scales along the side
• FishBase adds 3 to 4 dorsal spines with 14 to 20 soft rays, and 2 to 3 anal spines with 4 to 7 soft rays

Colour also depends on light. Wikipedia notes that goldfish make pigment in response to light, and a goldfish kept in the dark gradually turns almost grey. A pale goldfish from a dim tank is not necessarily a different fish.

Most wild goldfish are 12 to 22 cm (4.7 to 8.7 in) long, with some reaching 41 cm (16 in) (Wikipedia). USGS gives the same range in standard length, 120 to 220 mm with a maximum of 410 mm, and says wild fish usually weigh 100 to 300 g.

The maximum figures in the sources do not agree, so here they are side by side:

• FishBase: 48 cm total length and 1.6 kg
• Wikipedia: longest recorded 48 cm (19 in), in the Netherlands, as of April 2008
• USGS: up to 59 cm total length and 3.0 kg under ideal conditions

In captivity, Wikipedia says goldfish can live beyond 10 years, and FishBase records a maximum age of 41 years. For the record fish and the giant hybrids from carp lakes, see our biggest goldfish page.

The goldfish is one of the oldest domesticated fish. Wikipedia gives the timeline:

• Tang dynasty (618-907): a natural gold mutation appears
• Song dynasty (960-1279): selective breeding is established
• Ming dynasty (1368-1644): indoor breeding begins, allowing forms that could not survive in ponds
• 1603: goldfish reach Japan; 1611: Portugal

Today Wikipedia counts about 300 breeds recognised in China.

The sources disagree on North America. Wikipedia says goldfish arrived around 1850, but USGS dates the first recorded US releases to the late 1600s and lists early state records such as Massachusetts (1833), New York (1842) and California (1865). The USGS dates come from its introduction records, so they are the better guide to when goldfish were first in US waters.

Goldfish are not a food fish. FishBase describes them as edible but rarely eaten, and lists their main value as aquarium and ornamental fish, with some use in fisheries and aquaculture. Pet goldfish are raised for looks, not under food-safety rules, and wild goldfish live in whatever water they were released into.

We do not recommend eating a pet goldfish. If you are thinking of eating any wild-caught Carassius or carp, check your state or local fish-consumption advisory for that water first, and if anyone feels unwell after eating fish, contact a doctor or Poison Control (1-800-222-1222 in the US).

Released goldfish do real damage. USGS records them in every US state and territory and says foraging goldfish stir up so much sediment that aquatic plants can die back. Wikipedia adds that released goldfish are an invasive pest in parts of North America and Australia. Rehome an unwanted goldfish through a shop or club instead of releasing it.

The idea that goldfish remember for only a few seconds is wrong. Wikipedia cites research showing a memory span of at least three months and the ability to tell apart shapes, colours and sounds.

For keepers, the temperature numbers matter most: Wikipedia gives 20 to 22 C (68 to 72 F) as ideal, says fancy goldfish are at risk below about 10 C (50 F), and warns against water over 30 C (86 F). FishBase lists a pH range of 6.0 to 8.0.

FishLens identifies fish from a photo. For a wild or pond fish that might be a goldfish, a carp or a hybrid, photograph the head from the side so the mouth corners show, and a second shot of the dorsal fin. Barbels and a long dorsal fin with a serrated front spine are the two things that settle the question. For look-alikes in general, see common fish look-alikes.

Research and drafting for this page were assisted by AI and checked line by line against the sources listed below. Every number names the organisation it comes from, and where sources disagree we say so instead of picking one silently. Prices are shop listings we checked on 25 September 2026; they change, so confirm before you rely on them. If you find an error, tell us and we will correct it.