Large pH drop?
I have a 125 planted tank with quite a few fish. It runs two canister filters and has a Digital Aquatic pH controller for pressurized CO2, and moderate light. I keep my pH at 6.70 during the photoperiod. At night I turn off the CO2 and turn on an airstone. My pH goes to 7.35! I have just done a two-point calibration of the probe and checked these figures with an ATI chemical test kit.
That sounds like a very large change in CO2 content from day to night. It is consistent, in that I see it every night for weeks. The fish are very happy and the plants grow well without algae.
Can this be right? Am I tempting fate? I don't recall my KH, but it was nothing weird last time I checked, maybe 8-9.
Thanks for your ideas,