Apparently - this is what I have read everywhere - that "pockets" form in an aquarium under the compacted sand that is under the rock (or can). Now in the ocean, the reef really doesnt tend to shift much, and if it does, the current carries anything away almost immediately. Then if I were to use eggcrates, there would not be sand under my rocks sure - but there would also be spots of water where no circulation is getting to. Then I REALLY do not like the sound of the rock on the bottom of my tank. I dont want to scratch it all up and if something should knock it over (the rock), it stands the chance of cracking. Then I thought about 1/4 inch thick acrylic and was worried about water getting underneath of that and getting no water movement to it. So I just thought that i would get it cut as close to the size of the bottom as possible and then sealant the thing together.
It's going to be a longgggggg process, but oh well. I can take it off later and I dont have to worry about a starfish or urchant toppling my rock over (I dont stack it back to the wall - I like to leave room for my snails to get all over the glass) and it smashing into the bottom of my tank at a jagged part.