I got curious and tested my PH and Alk last night at 10 pm. Acid had been circulating for about 7 hours.

PH had dropped from 8.0 to 7.6.
Alk had dropped from 230 to 180.

I ran a quick PH test this morning.

PH had risen from 7.6 to 7.8.
Didn't have time to test alk.

I am getting a bit of air in the suction side of my pump and my return flow is bubbly. I assume this could be having an aeration effect, explaining the PH rise. I was reading Ben's high PH article again, and will probably just keep an eye on it for awhile to see if the PH rise levels out. If it gets above 8.2, I'll add acid again.