Little goldfish can live for years in a small aquarium without growing much.
Turned loose in a large body of water they multiply enormously and often reach a foot in length. In a few generations, ordinarily, they lose their bright colors and revert to the greenish bronze of their wild ancestors. The goldfish and the carp, both natives of eastern Asia, have become naturalized in many other parts of the world and are so closely related that they hybridize readily. Very hardy, they can endure extremes of temperature and eat almost any food, both plant material and animal life. They have the same general habits as carp and join them in roiling the water.