EDIT - See below link for a thread featuring another indoor koi spa by Karl:
https://www.koiphen.com/forums/showthread.php?t=101931
I built this indoor prototype koi tank in 2004. Since then I've built nine more. Each time there have been improvements in design and usability. So it was time to take my first one and work out a way to improve it.
This is what it looked like in 2004: