Long time update:
Tickled to death lately. I finally have crystal clear water. Combination of proper mechanical filtration plus 900gph going through a UV light. It's been working great this year, proof in the pudding when I clean the filter and the slight cloudiness goes away. The stones /items you can see in these pictures are 5 feet down on the bottom.
The two koi I bought last year are thriving (the big white ones). I brought home 4 new 3" koi on Monday and they seem to be getting along fine. I feed them often, twice a day for 2 days and then 24 hours no food due to my work schedule.
Finally got some plants too, that seems to really help the new generation of Goldies, which I find undesirable these days. I think it'll be a continual removal effort for a couple years.