Egg Crate Under Rockwork ?

[hippo!]

I use it on all my tanks. Cheep insurance IMO.

[viperfish]

a couple of inches of sand will cushion the rocks from creating any stress concentration on the glass. My only fear with eggcrate is that it's just another place to trap debris that can't be siphoned out and sand sifters won't be able to get to it. I guess it would help in the event of a rock slide but I've never heard of stationary rocks on a sandbed cracking glass.

[Aquattro]

I would never put rocks on sand again, I had a tower collapse as the sand shifted under it. Probably induced by some livestock, but it was a mess. Didn't hit glass, but from now on my rock sits on solid footing and sand goes in second.

[viperfish]

I stack mine very carefully, and a little bit of DD putty between them ensures nothing is going to move. I also place some putty anywhere a rock might touch the glass on the back to reduce the stress concentration.

[mark]

when I had a DSB built boxes with egg-crate and zipties for the rock to sit on so the bottom 4" wasn't buried in sand.

With the new tank and BB, rock just sits directly on the glass.

[DiverDude]

Some interesting points have been made.

I was only planning on putting small(ish) sections of Egg Crate (EC) under the rock and not over the entire bottom. I'd like snails, my sea star, bulldozer shimp/Goby to be able to dig away without the impediment EC might cause.

The though was that where there was rock, the EC would displace stress and PREVENT any/all of the aforementioned critters from undermining it and causing issues.

The acrylic is a really good idea too as is the ABS -but I've been told not to put ABS in a tank but I'm sure a few bits under sand wont' hurt anything.