Peat only has a minor influence in my limited experience. If your pH is high it generally means there is a reasonable amount of buffering in the water, so your best bet is to lower it by filtering the water before adding it to the tank. look for RO (reverse osmosis) on the forums and see how people do it. You might be able to DIY a system that's fairly cheap.. commercial systems are hundreds of bucks, and you might be OK with a simpler water filter rather than full on RO.