Rodney, thanks for all your help over the years. I am currently dealing with a few lethargic koi in my 3800 gallon, 26 year-old pond. I only have 5 koi but they are all pushing 30" or more. My oldest is 32 years old. The others are all 15+ years old.
I don't spend much time on koiphen but its always my go-to site for filter upgrade ideas and koi health problems. In the past when I've had koi health problems, I've turned to PP. I came back to koiphen this yesterday to see if there were any updates to your PP protocol. I read thru this entire thread twice over the last two days. I decided to do a 2 ppm treatment every 4 days over the next month to (hopefully) squash what the pest might be. I generally try to avoid pulling fish. It's time consuming, heavy work (about 20 lbs each), hard on the koi and in the end I almost always reach for PP anyway because its so broad spectrum. I'll monitor the fish thru the process. The first dose turned brown after 2 hours so I redosed with another 1 ppm dose. The second dose turned brown after 3 hours (5 hours total). I think that's an indicator of how clean I keep my pond. I'll add HP in an hour or so and plan on redosing in 4 days from now.
I also appreciated the water regeneration ideas using PP. I read about that years ago but with the persistent low rainfall in California, anything I can do to save water is a worthy exercise.
I truly appreciate your scientific approach to the PP treatment. I don't have enough chemistry understanding to follow the chemical processes but appreciate that you do and share your knowledge so eloquently and your time so generously. I also have a PhD (electrical engineering/mathematics) and went to USC engineering school as an undergrad. You're 1/2 generation older than me. I worked with a fellow that also got a PhD (electrical engineering) at USC about the same time you were there. He studied radio propagation and antennas. I know you weren't doing that but perhaps you cross paths with him: Ken Brown.
I truly don't understand some of the nay-sayers in this threads. Legitimate discourse is helpful to everyone so we can all grow and understand, naysayers with (what appears to be) a vendetta are unhelpful and nasty. I generally skip over their posts. It always boggle my mind trying to understand why they bother. Thank you for keeping it civil.
Cheers! Miguel (on the central coast of California)