it will lower your PH if you don't soak it first.. the tannins will leech out and turn your water brown and depending on your kh can lower your ph alot or a little..Most likly it will not affect it much especially if you do frequent water changes. I do recoment soaking it in a big rubbermaid tub with hot water for a couple of days though.. You will be amazed at how brown your water can get if you don't.