Just saw you stated you add to the ATO. I used to drip in that but realized the DT doesn't get anything until ATO kicks in and that will cause it flucuate. I drip into the return chamber.I measured before and normally add 5ml calc and 10ml Alk. So I drip at slowest rate and measure again in a few days. Will do that a couple times to ensure nit dosing to much.