The best thing to do is get hardy fish that can tolerate a wide range of pH levels or fish that prefer a high pH like African cichlids. A steady pH is always far more desireable than the "perfect pH" for a fish. Here's the catch--once you start messing around with water parameters, you have to do it with every water change.
I have tried peat moss, driftwood, and chemicals. The only way I have been able to effectively lower the pH in water is to use distilled or RO water. I still use it; I buy 10 gallons a week from Walmart (the only place with a water machine in my area), and mix in trace minerals before I use it.