Simular problem in the Chem forum low ph, it sounds like a testing eror unless you doses vinigar or selzer water. If you go there, and scroll down a bit you can read it. It is about have way down on page 1.
I agree that it is almost certainly testing error. Reef tanks do not typically get that low. The pH may be low, but is not likely that low, and I'd confirm the pH another way before taking any action other than more aeration with fresh air, which never hurts and can solve low pH problems.
ok, I have the skimmer running and I thought that would be enough. It test 7.4 in two tests I have one test called jungle, its a strip dip test and then I have the aquarium pharma.. and they are both at it. I test calcium and alk with salifert.
If you have excess CO2 in your home air, a skimmer will drive CO2 into the water, not out of it, and thereby reduce the pH. The aeration needs to be with "fresh" air. People often miss that part of my sentence. Perfect aeration with normal air will prevent any pH change at all and will peg it at about 8.2-8.4, depending on the alkalinity.