Well I added top soil to my substrate. I left about an inch of clay/rock on the bottom, then added an inch or so of soil. However there was a bit of water in the tank, and there was enough pressed out of the clay apparently to turn my wet soil into total muck. Man what a mess :S. Once I put the river rock on top like before I replanted the tank, this time with a it of organization
. This was a sort of trial run for when I add soil to my 20G... and I learned to keep the soil dry when placing!