Wait, How Big Can Goldfish Get? A Very Serious Investigation. Lydia Wang. Last Updated July 14, 2021, 12:30 PM. Photo: Lyu Ming/China News Service via Getty Images.

How Big Do Goldfish Get? A Fantail goldfish. Goldfish can grow to 10 inches or more in ponds, but are unlikely to reach that length if they are kept in an aquarium. EuToch/Getty Images ...

This goldfish isn't native to the area, but they aren't invasive, Houck said. He and Scott Robinson, who was working with him, put the fish back in the water after they took a couple of photos.

A massive "Megalodon"-like goldfish caught last year in Pennsylvania has led to a new warning from the U.S. Fish and Wildlife Service -- don't let your pet fish loose in the wild.