In general, goldfish can survive quite happily in outdoor ponds across the US, but there are a number of practical and legal considerations you should examine before you dump “Bubbles” and all her friends in the backyard. First, goldfish are members of the carp family and native to Asia. In the US, they are invasive species that can grow very large, destroy habitats and out-compete native fish for food and space. In fact, it is illegal across the US to release goldfish or even flush them down the toilet and failure to comply can be punished by substantial fines. Artificial outdoor ponds, then, that are not connected in any way to natural waterways and will not overflow to carry residents off into the great blue beyond, are the only acceptable outdoor digs for any type of non-native fish.
If you’ve got a backyard ornamental pond with an average depth of 3’, moderate sized plantings around the edges and a few floating plants to provide shade, then most goldfish are likely to be quite happy. Not terribly picky, goldfish are happy to eat insect larvae, tadpoles, bugs, as well as aquatic plants like duckweed and even algae. With their bright colors, they will need cover to hide from sight predators like cats and herons, and they’ll need some deeper parts to retreat to on hot days and when winter leaves a skin of ice on the pond. In fact, goldfish can overwinter outdoors in most regions of the US if pond conditions are right. Common goldfish, Comets and Shubunkins are all hardy and adaptable varieties of goldfish and can make beautiful additions to your outdoor pond. However, highly bred and specialized types of “fancy” goldfish are not great candidates for living on the edge of the wilds. Fantails, orandas, black moors, celestials, and pearlscales are all “fancy” types that refer to rounded bodies, double tails, protruding eyes and other features that are attractive to some owners but render them helpless outside of a highly protected fish tank. Double tails and ping-pong-ball bodies mean they swim slowly and sometimes have a hard time even remaining upright. Bulbous eyes leave fish unable to see what dangers lurk nearby while the eyes themselves are vulnerable to serious damage, even from simply bumping into a rock. It is a kindness to keep these over-bred specimens in an appropriately artificial - and safe - environment.
