So do you attach the egg crate with superglue or epoxy? I'm sure it's cheaper to make the racks like that anyways.There are many out there that work just fine if your tank is 1/2" or less in thickness. There are very few that work well that are 3/4" thickness or more. I fall under the latter ofcourse because it makes sense to make things difficult. What to look for are strong magnets for stability, and stability and stability. Nothing worst than a snail being able to knock it down.