Lil Koi Dearie-
When I read, I read for comprehension, slowly, absorbing details and sometimes moving my lips. I understood why you didn't WISH TO put in bottom drains...the reason I suggested a compromise... penetrating the liner above your ground water and extending down from there inside the pond to where it could act as a suction drain. This is a compromise. It will work better than a pump in the bottom. (Are your lips moving?)
The depth of 5'6 should be adequate for the survival of your koi through winter, like you said. Got it. Bringing them in for the winter may help them thrive but will have it's own set of drawbacks. Have fun.
Sheesh! This is inelegant, ineffective, inside out and backwards. I said something a bit more positive in my post that you didn't read.
Completely unneccessary and robs the pumps volume for misapplied velocity.
There is nowhere near enough bio filtration in this falls. See my first post for positive comments.
There must be a good reason, like starting work at 530am, for not doing this EVERY day, like me.
Your plant ideas will destroy the possiblity of using these tubs to actually filter your water.
Three good, four better. Old convention was more than two feet of media height to get the benefits of degassing. You want as much flow through this as you can get, generally.
Is this your name? Good luck with your upgrades.