Someone here mentioned using it.
My guess drops per gallon. Do you use pool test strips to measure ph ect? I do.
Lots of calculating dilution ratios for final test.
I've used vitamin c powder, maybe 1/2 teaspoon per gallon which then gets mixed 16:1 by syphon.
Lowered it from 7 to 5.5 or so, will take pics next time.
Put 1 vitamin c in gallon of water & see how drastically it lowers ph.