Mine does not usually vary more than about .15.
I get 2 swings per day, 1 when the MH shut off at 7 pm and the ph drops until 9 pm when the Kalk ATO starts up. The ph then slowly raises until 9am when the kalk shuts off and it starts to fall until 11 am when the MH fire up then it raises all day. I just recently expanded my mh by 1 hour on each end so this should make the dips smaller.
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