Early in the thread someone said to pick up both pH up and pH down. I would disagree with this statement. Depending on your tap water will determine what pH product is correct for you.
Example : My tap water comes out at 7.0 or 7.5 depending on the day. All I need is pH down. Should I decrease my solution to far all I have to do is add more tap water to bring it back up again. Simple as pie and saves you a couple bucks in the process.
Also take it easy with that pH adjusting solution. Usually all I use is a half a cap full and that is usually adequate enough to drop it from 7.5 to 6.0-6.5.