should i worry about putting anything under the sand?

[kien]

I have a sheet of acrylic under each of my structures. If nothing else, it at least provides relief from those sharp rocks and preassure points on the glass. I'm sure the glass could take it but like you I'm paranoid like that

Actually, it was handy to have the sheets of acrylic underneath while I was in the process of aquascaping. This way I could slide the sheets around easily with rocks/bolders and all.

[whatcaneyedo]

I wish I had the forethought to place a sheet of egg crate under my rocks. I have several fish that like to move my sandbed around and some egg crate would help to keep at least some of it in place over the bottom glass so that I didnt have bare spots. Plus reducing pressure points created by the rockwork would help me sleep better at night.