Biggest Goldfish: Records, Real Size and Giant Hybrids

The longest goldfish in the Guinness World Records book measured 47.4 cm (18.7 in) from snout to the end of the tail fin. It belonged to Joris Gijsbers of Hapert in the Netherlands and was measured on 24 March 2003 (Guinness World Records). That record is for length, not weight.

Other reported big goldfish, all from Wikipedia's goldfish article:

• April 2008: a 19-inch (48 cm) goldfish in the Netherlands, which the BBC believed to be the largest in the world
• July 2010: a 16-inch (41 cm), 5-pound (2.3 kg) goldfish caught in Poole, England
• November 2020: a 15-inch (38 cm), 9-pound (4.1 kg) goldfish found in Oak Grove Lake, Greenville, South Carolina
• 'Goldie' of Folkestone, England: 15 inches (38 cm) and more than 2 pounds (0.91 kg)

Much bigger than a bowl suggests, but not monster-sized. Wikipedia gives 12-22 cm (4.7-8.7 in) for wild goldfish, with some reaching 41 cm (16 in). USGS gives the same 410 mm maximum and says wild fish usually weigh only 100-300 g. The common goldfish can grow larger than 12 inches (30 cm) in a pond (Wikipedia).

Tank size matters, though not the way the old saying goes. Wikipedia calls it a myth that goldfish grow only to fit their tank, while noting that tank size does influence growth rate. Wikipedia's space guide is about 10 US gallons for a young goldfish and 20 gallons for each mature common or comet goldfish.

The plain, single-tailed common goldfish. Wikipedia says it can exceed 12 inches, and the comet, a long-tailed variety bred from common goldfish by Hugo Mulertt in the United States in the 1880s, is described as slightly smaller and slimmer. Fancy, round-bodied varieties such as fantails need about half the space per fish (10 gallons against 20, Wikipedia), which suggests a smaller adult size. The Guinness record fish is listed simply as Carassius auratus.

Photos of much heavier orange fish from carp fishing lakes regularly go viral as 'the world's biggest goldfish'. We could not open a primary report for these catches, so we do not repeat their weights here. What we can say is how to check one:

• Barbels: goldfish have no barbels; common carp do (USGS; see our common carp page). An orange fish with barbels is not a pure goldfish
• Hybrids: goldfish commonly hybridise with common carp, producing fish intermediate between the two (USGS), so a huge 'goldfish' with carp-like features may be a hybrid
• Dorsal fin: a goldfish has a long dorsal fin of 15-21 rays with a hard, serrated spine at the front (USGS)

A side-on photo with the head in focus is enough to check barbels. FishLens shows its top matches and how confident it is, which helps when a fish sits between two species.

Not a goldfish: the heaviest one reported in the sources above is 9 pounds. Fish that reach or pass 1,000 pounds include the ocean sunfish, covered on our Mola mola page, which reaches about 1,000 pounds. Among freshwater giants, see the arapaima and the alligator gar.

We found no published price for record-size goldfish. At the other end of the market, Wikipedia notes that comet goldfish are cheap enough in North America to be sold as feeder fish and given away as carnival prizes. Price for a large pond goldfish depends on the seller, size and variety; ask for its length and age rather than paying for a 'giant' label.

Wild goldfish in lakes and rivers come from fish people released. Goldfish were first released in North America in the late 1600s and are now recorded in all 50 US states (USGS). USGS says foraging goldfish stir up sediment and cloud the water, which can kill off aquatic plants. If you can no longer keep a goldfish, rehome it through a shop, club or rescue rather than a pond or stream.