You realize GhostFish that you have already had an epiphany. You understand that keeping large riverine carp is something best done in a pond system designed for them.
You definitely should consider joining a koi club in your area. At
AKCA - Associated Koi Clubs of America - Welcome To The you can find listings of clubs that are affilated with Association Koi Clubs of America.
Once in a club you can borrow books and tapes for your research. You may be able to borrow additonal books and magazines from other club members. You might want to check out the books, magazines, and videos in this list. I definitely suggest reading at least the first four of the books.
Reference Material On Nishikigoi And Nishikigoi Ponds - KoiShack
follow that classic advice....build a koi pond system once...much cheaper that rebuilding it many times later.