I got my piece which is about 12 inches wide and 12 inches tall. It is a Traingle shaped piece of Malyasyian driftwood that I got from the corporate beast PetCo for $9. It sunk right away, but I have been boiling pots of water and pouring them in my sink since the piece wont fit in a bucket. I submersed it in boiling water and let it sit over night twice allready. Now on my third time it is still discoloring the water slightly. The tannic acid isnt harmful though, and will only discolor your water a slightly amber color. I will probably boil it and let it sit over night once more, and if it discolors my water I am sure (Actually, I hope) it will only last through a couple water changes.
Hope this is helpful.