Can a Goldfish Really Grow to 30 Pounds?

Young children everywhere now have a new image to fuel their nightmares about what happens to their pet goldfish after they flush it down the toilet. A photo of an alleged 30-pound, bright orange carp, caught by a French fisherman, has surfaced – to much speculation.

Could a goldfish really grow to that size?

The fish in the photo actually appears to be a Cyprinus carpio, usually called common carp or koi, which is distinguishable by the two short whiskers (called barbels) surrounding its mouth and large scales covering its body, according to the New York Department of Environmental Conservation (DEC). The fish also has dorsal (back) and anal (bottom rear) fins, as well as a single thick fin running down its spine.

The fisherman in the photo, Raphael Biagini, reportedly claims the carp he caught and posed with for a photo (before setting it free back into the water) weighed about 30 lbs (13 kilograms). Biagini caught the mega fish at a lake in the south of France.

It seems a carp could really weigh that much. The world's largest carp on record weighed in at 94 lbs (42 kg) and was caught in 2010 in Rainbow Lake near Bordeaux in France, according to The Daily Telegraph, a U.K. newspaper.

The previous record-holding carp, which weighed 88 pounds (40 kg), was caught in Rainbow Lake in 2007. (The fisherman named his catch Kylie after the popular Australian singer Kylie Minogue.)

While it seems record-breaking carp come from France, New York's carp can grow to weigh more than 40 pounds (18 kg), according to the DEC. The largest carp found in New York waters weighed in at 50 pounds 4 ounces (22 kg).

Goldfish (Carassius auratus auratus) are part of the carp family but do not have barbells around their mouths. They vary in their fin configuration, coloration and in their body size, which is directly influenced by their environment.

When they are kept as pets in small fish tanks and aquariums, goldfish tend to stay about 1-2 inches long and never grow larger than 6 inches (15 centimeters), according to the DEC. However, in the wild, goldfish often reach 12 to 14 inches (30 to 35 cm) in length.

Although pet goldfish are usually amber-hued or white with scarlet spots, most wild goldfish are a dull olive green color that allows them to blend in at the bottom of ponds and lakes when hiding from predators. [America's Favorite Pets]

The title of largest pet goldfish goes to Goldie, who was 15 inches (38 cm) long, 5 inches (12 cm) wide, and weighed over 2 lbs (0.9 kg) in 2008, according to the BBC. Goldie's owner told the BBC that the fish was only an inch long when she bought it for 99 cents, and 15 years later it had ballooned into a record-breaking size, despite being kept in a small tank.

• What's the Most Popular Pet?
• Why Are Asian Carp So Fearsome?
• What's the Biggest Freshwater Fish in the World?