The thread about almond leaves got me to thinking. Are there other leaves that would tend to lower pH besides these two? I use small oak leaves and although they don't seem to have much effect on my pH, I like the way they look, they last quite a while, and my apistos and other fish seem to enjoy them. What other options are there, and are there any that should be avoided? Seems to me I read somewhere that beech leaves work well.