[geekdafied]

um I think you're leaving out some steps. The purpose of the egg crate is to lift everything off of the bottom of the tank via 1/2" or 3/4"pvc pipes and then nylon screening(window screen) placed on top to prevent the sand from falling through it. Thus making a plenum. I would recommend using some kind of rigid air tubing to make and updraft tube and attach a powerhead to it so it will pull water through the substrate. You cant use just any sand though. It needs to a mediu, rought .7 tp 1.3mm sand. sugar sand will fall right thru the sceen.