Can KH be too high?

[Angie Jones]

I use baking soda to keep my KH between 8-10 drops on the API test kit. I tested recently and my KH was at 13 drops and I have a friend who once had her KH at 17 drops by accident. We all know the danger of too low a KH level, which brings me to my question. Is there any danger to the koi of having it too high?

[richtoybox]

KH is a measure of the bicarbonate ion, at least in our ponds, and bicarb will stay bicarb, until there is either an excess of hydrogen ion (acid), which is most likely, or an excess of hydroxide ion causing the pH to rise above the 8.3 range. Either way, it chemically reacts to remove the acid or base ions. So no there is not a problem with high KH. While I was ponding, I had two ponds, one 4000 gallons and one 3500 gallons and if the KH went down to 100ppm, about 6 drops, I would split a 13 pound bag between the two ponds raising the KH to the point that I wouldn't even run the test to completion.