I put loads of bogwood in my tank and I pre-filter water change water through peat. The important thing is to let the peat-filtered water stand for a bit to let all the CO2 bubbles escape as otherwise it causes pH swings.
I also have CO2 but that doesn't have a huge effect on pH because my water is so hard.
By these means I've got my pH down to 6.8. The important thing is to go really slowly - 10-15% water changes with peat-filtered water per week is good.
