Once you've mixed your
nutrients, and adjusted the pH if needed, you shouldn't need to adjust the pH more than once a week. If your adjusting it daily, somethings wrong somewhere. I have been using earth juice dry pH adjusters, and bought the smallest (one pound) containers. Those adjusters have lasted me well over a year, and cost about $10 ea (shipping not included). General hydroponics makes dry pH adjusters also, and I will be trying them next because the new hydroponics shop (the only one in town) has them in stock, and run something like $11 for 1.5 pounds, and I wont need to pay for shipping because I can get them right here in town.
P.S.
If you don't already have some, you'll want to get some pH up to have on hand as well.