Peat moss is another natural acidifier, which can be placed in your tank. Seachem makes some buffers that will lower your Ph as well. I have been using the buffers and have never had a problem. I also have a lot of wood. Between the two my Ph is 6.6. If you can't find these items in your lfs, then check out an online store like www.liveaquaria.com or www.bigalsonline.com.