We built a (roughly) 350g, plastic lined pond earlier this spring. It varies from 16-26in depth from the surface with about 18in underground at the deep end, and it has 6'x4' surface area. We're colder than normal for this time of year and water is at 55 F today at noon. This winter I brought in our fish, a young koi and a young goldfish (both about 4-5in) from a small pre-formed pond because we had a much colder winter than usual and during one cold storm I lost a small koi. I guess I was panicked when I brought the other two inside. Now that they are inside, I want to introduce them to the new pond under the best conditions. I've been lucky in having several small ponds over the years with thriving fish, but I'm trying to do things by the book this time. Also, can I get another baby koi and/or "feeder" goldfish? Do koi appreciate koi friends over goldfish and vice versa?