Drift wood prep for aquarium? (For PH buffing)

[adamxaotmic]

My PH has crept up to about 7.4 and instead of having to add PH down I was thinking of using some drift wood as a PH buffer to naturally lower my PH.
I live close to the beach so acquiring some wasn't hard. I've read reviews that say to properly clean it before putting it in the aquarium you need to boil it which will remove most of the tannins. But aren't the tannins what I want in order to lower the PH?
I was also wondering on how to submerge the wood. I don't really want a bucket of water with wood in it sitting in my apt for the next couple weeks. I was thinking of using some kind of weight. Any suggestions?