My pH used to be about 7.5, the same as my tap water. Now it keeps raising to like 8.3 and I have no idea why. I use play sand which I vacuum every week and just added fresh sand on top of it to put plants in my tank. I washed all the plastic plants and replaced the filter other than the biological media. I use rocks that I tested when I collected them to see if they would have a reaction to something from the API test kit (it was years ago, don't remember exactly what the procedure was) to see if they would affect my pH, and I didn't get a reaction so I've always had them in the tank. I used to have driftwood but I don't at the moment, I'm waiting for some I ordered to come in. I have 7 small live plants right now. Should I add more plants, or consider using CO2? Or will the pH be fine after I put the driftwood in? I just don't understand why it's so high in the first place.