I've been contemplating digging a pond and keeping some fish and I was wondering what is the best fish for a freshwater pond?
There are a few that come to mind, and if you get the common variety they are pretty cheap.
First, you have the goldfish,. There are a few different types of breeds and each have their pros and cons, but overall they are pond fish that can survive winters (as long as they are a year or two old), and can survive throughout the summer as long as proper aerate and the pond is deep enough for the water to stay cool enough.
Secondly, you have the koi fish. The aren't that may breeds, but based on their coloration you can spend anywhere from a few dollars per fish up to thousands if they have a more rare coloration. If you want bigger fish than goldfish, I would recommend these since they get longer and wider than goldfish.
There are also others that are kept, but for beginners I would recommend these two types of fish due to their ease of care and high availability in almost every city that has a fish store.