The goldfish is a freshwater fish. It was one of the earliest fish to be domesticated
A relatively small member of the carp family (which also includes the koi carp and the crucian carp), the goldfish is a domesticated version of a less-colorful carp native to East Asia. It was first domesticated in China more than a thousand years ago, and several distinct breeds have since been developed. Goldfish breeds vary greatly in size, body shape, fin configuration and coloration
(various combinations of white, yellow, orange, red, brown, and black are known).
Goldfish are popular pond fish, since they are small, inexpensive, colorful and very hardy. In an outdoor pond or water garden, they even survive for brief periods if ice forms on the surface, as long as there is enough oxygen remaining in the water and the pond does not freeze solid.
Common goldfish, shubunkins, sarasa, comet and some hardier fantail goldfish can be kept in a pond all year round in temperate and subtropical climates.
Ponds small and large are fine in warmer areas (although it ought to be noted that goldfish can "overheat" in small volumes of water in summer in tropical climates). In frosty climes the depth should be at least 24” to preclude freezing. During winter, goldfish become sluggish, stop eating and often stay on the bottom of the pond. This is normal; they become active again in the spring. Unless the pond is large enough to maintain its own ecosystem without interference from humans, a filter is important to clear waste and keep the pond clean. Plants are essential as they act as part of the filtration system, as well as a food source for the fish. Plants are further beneficial since they raise oxygen levels in the water. A small amount of algae is also a very nutrionose foot source.
A fully grown Goldfish comes to about 12” to 14”, depending on the Invoirement.
As smaller your pond, as smaller the Goldfish.
Do not buy to big Goldfish if you have a smal pond.