Goldfish live in temperate bodies of freshwater and have a preference for murky conditions. This breed is hardy and can endure temperatures near freezing, provided their habitat has enough oxygen and remains unfrozen. In the winter, outdoor goldfish exhibit dramatically decreased activity and remain in this state until spring.

Goldfish are the descendants of domesticated carp from ancient China. Genetic mutations and selective breeding are responsible for the striking colors of goldfish, which originally featured shades of gray, silver and olive. Wild goldfish subsist on a diet of crustaceans, insects and plants. Intelligent creatures, goldfish can differentiate between individual humans and are able to be trained through positive reinforcement.