pH dropping fast

reefm · Jul 21, 2017

I'm at a loss as to what's causing this pH drop. pH was previously hovering in the 7.9-8.1 range - it's also not a measuring issue as I see my zoas have closed up. I calibrate the Apex probe monthly.

Have 2 powerheads pointing to the surface and windows are open for 2-3 hours daily, on AC circulation otherwise. Skimmer is skimming normally (can't run line to outside). The small spikes in the graph are from my ATO, dosing Kalk - no dosing change either. The large drop on 7/15 was the probe calibration

SG 1.026, Alk 11.2, Ca 440, Mg 1280, PO4 0.03, NO3 8

Any ideas/recommendations?

Randy Holmes-Farley · Jul 21, 2017

I suspect that is calibration drift. Try recalibrating.

LobsterOfJustice · Jul 21, 2017

How old is the probe?

reefm · Jul 23, 2017

thx for the feedback!

Something was interfering with the probe. I disconnected the probe and ran it outside the cabinet to a cup of my tank's water, immediate 0.2 pH jump. Then back into the sump probe holder but without routing the cable the way it was before, pH stayed up.