Hello all. I'm about to close on a house that has a spring fed pond on my property. I have always wanted a koi pond. Do I need any thing special for a large pond. The pond is a little bigger then a NHL arena. I don't know total depth but from the doc I reached 4 feet and that's only about 8 feet from the edge I'm sure it's close to 10 feet in the center if not deeper. About how many koi can be kept in a pond this size if at all?