Sorry, I totally disagree with the approach of just adding Xppm of PP. We put in PP in order to get the ORP levels to the 500-550mV range that is oxidative enough and long enough to kill parasites in the pond system, and on the koi, without frying their gills.
You can not know if the water is not quite hot enoug, just right, or too hot......and for how long...without using a calibrated ORP meter. Using an ORP meter we can have emphirical measurements before, during, and after the PP treatment. No guesswork and therefore minimum risk for the fish.
In the States we can get an ORP meter that can be calibrated for around $100. It, like a microscope, should be part of all koi keeping kits.
