Egg crate does being to sag a bit at 30", that's my main reason I have not put egg crate on top of my tank, I just leave the glass top open. I'm still going to switch, just trying to figure out how to make it sturdy enough to support it's own weight without being able to use most of the rear of the tank (HOB, overflow, pumps in way). If you can get 4 sides of support on the egg crate, you may be okay.