OP, If you had rubber padding like for carpeting you may as well have put it right on the floor. There is not enough rigidity to that stuff to help take out unevenness in the floor. In that case I would have put down 3/4" or 1" plywood to extend beyond the frame of the tank, then pink board. Depending on the floor it still may not have been enough to prevent this damage. In the case of my 125 with the 1x6" floor joists I laid down 3/4" plywood to place my stand on then the foam and tank.
