I have been tossing around the idea of using egg crate for aqua scaping. what I plan on doing is using egg crate to put rock on and will use pvc caps and drill a few holes in the pvc caps and lay them on the glass and then have sand under the the egg crate. then use rock rubble to hide the eggcrate around the bottom of the rocks where it can be seen in front and on the sides where it's viewable through the glass. any down falls with doing this? I might add some more sand if I think it needs it. I do realize that might start a small cycle also. but not to much as I do not want to deep of a sand bed. since I heard a deep sand bed can cause more problems. for cuc I do have a few snales, 2 emerald crabs I think. they hide on me. and a sand shifting star fish and 2 brittle stars. they hide all the timer. the caps I plan on using is 1 in schedule 40 pvc cap.