It begins...

[squibege]

Eggcrate will not be covering the entire bottom. Current plan is to prop small pieces of it as a base under the rocks on pvc columns so I can zip-tie the bottom rocks down securely, and the nooks and crannies at the bottom aren't completely hidden by the sand bed

[Myka]

I think the structure on the right would be good if you just take off the top rock. Fwiw, I wouldn't use eggcrate at all. Fish/flow will expose it, and you'll be hating it.