Where do you get your CaCO3?
Can you elaborate a bit as to the negatives of excess K?
Why do you steer clear of sodium based products such as baking soda?
CaCO3 happens to come from work, tons of it used during the cold weather months.
Can be purchased from Ebay, Alpha Chemicals I believe, it is cheap.
Excessive potassium, is it a myth, I can't say.
With higher alkalinity it is claimed as a problem.
I tend to steer clear of problems even if they could be a myth.
Sodium is not required by plants, why introduce it?
Lots of people use baking soda, I have in the past but no longer.
So how much KH/alkalinity is really needed in a tank.
.5dKH or roughly 8ppm of carbonate hardness is all.
Plants will appreciate a lower alkalinity anyway.