Planted Tank Guru
Join Date: Feb 2010
Location: Newbury Park, CA
Or attach the wood to a piece of slate, tile or even acrylic that is a few inches larger all around than the wood with stainless steel screws and bury it under the substrate. Works great and your wood is very hard to dislodge. Of course you won't be able to change the orientation of the wood easily so be sure that is just the way you want it.
Right now weigh it down with a few rocks, it water logs faster if it is completely submerged for some reason.