Ca & Alk. raising??

Chris C · Oct 31, 2015

Hi, the Ca and Alk. in my tank raised from 520 to 540ppm and 10 to 11dkH without any WC and dosing. Is it possible? Or should I assume they're testing errors??

Randy Holmes-Farley · Oct 31, 2015

Just testing errors, unless your top off water was tap water, in which case it might have come that way.

rufus2008 · Oct 31, 2015

Could be evaporation is the culprit.

Randy Holmes-Farley · Oct 31, 2015

That's true. You'd need to evaporate 4% (4 gallons out of 100 gallons) and not replace it for the calcium to rise that much, and 10% for the alkalinity.

That said, not many test kits will reproducibly distinguish 520 and 540 ppm. More would distinguish that alkalinity change, but if the kit uses drops and 1 drop = 1 dKH, one should expect the answer must be +/- 1 dKH.