04-
None of us will tell you that a bottom drain isn't neccessary; it is. The folks you are talking to may call us nuts. Yep. So nutty we have good ponds.
A bottom drain doesn't hook up to the skimmer.
If you are ready here are two maybes- order KoiKichi by Peter Waddington. Pay for rush delivery.
Or, go to the show in North Carolina May 4th, and learn something there.
Southern Koi Expo
Your contractors will not like this. I am one also. Houses, not ponds.