That is why I left mine alone even though the ph went up to 10ish. The fish were procreating, swimming eating, tads, water bugs etc. It has now, by itself self, settled back down. I was at a store buying junk to mess with the ph, a fish breeder, seller and I started talking after a long conversation I decided to wait it out. His thoughts lined up with mine, fry, happy fish, eating like hogs, tads, good plants why mess with it. I am glad I did nothing. NO KOI
Sometimes it is best to have faith in mother nature. But then again I have built my system to be as natural as possible with a bog filter system. Gravel and plants.