Alkalinity help

[Randy Holmes-Farley]

It may just be testing error to try to see such small differences, or it may be other small effects going on.if you are dosing nothing then the demand is very very low and very minor effects can add up to 1 or 2 dKH in a month or two. Nitrification, denitrification, dissolution of calcium carbonate in sand and rock where pH may be lower, top off water with traces of alk in it, even foods may have traces of alk.