I bought a plastic planter (no drain hole) yesterday and am going to put 3 varieties of VFT in it. I've mixed the media (1:1 sand/peat mix) and put it in the container. The container is pretty deep, so I put pure sand in the bottom about 4" deep to keep from using as much peat. Is this okay? Will the sand keep water in the bottom of the container from seeping back up into the growing media? Any other suggestions for my little container bog?