I like to keep my rocks off my substrait as much as posable but most of my rocks are large and heavy because I collected them in the sea.
Much of my new rock is hollow PVC with cement coating it. I am soon going to re aquascape and I will keep the rocks lifted off the gravel with these
structures. When it is in the tank under the real rocks, it should not be visable except for the column legs.
This first picture is of course the construction.
The thing cost less than a buck and took about an hour to complete

Thanks for the image.