The problem with messing with your natural PH is that it's very very hard to keep it at that level. For example...You treat your 10 gallon tank to get the PH to 7.0. You do a water change, and treat the new water in the bucket and add that to the tank (assuming you can measure out EXACTLY how much is needed to get the new water's PH correct), now the water in your tanks PH will swing as the new water mixes with the old. This creates PH swings and fish hate that more than just a low or high stable and steady PH. Unless you're trying to breed or keep a very specific type of fish, I would NOT start messing with your PH.