01-13-2008, 11:00 AM
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Egg crate, that plastic grid that's used to diffuse the light coming out of overhead strip lights in offices, is cut to fit under the area you'll be setting you're rocks up. By sitting the rocks on the egg crate, you assure that the weight of the rocks is distributed evenly over the floor of the tank, rather than concentrated on the three points where the rock touches. I mean, you wouldn't have any problems putting 60lbs of gravel in a tank, and this is the same thing - the weight is distributed so instead og a 60 lb rock putting 20-30 lbs of pressure onto three points (A stable rock will touch at three points minimum), you're looking at pressure more like 1 psi or less, depending on the footprint of the rock and the egg crate (1 psi for for a 60 lb rock with a 5x12" footprint of egg crate under it.)
The one thing that concerns me about egg crate is that whatever substrate gets down into it will have zero water flow, and has no reason not to become anaerobic. Now, this shouldn't be a problem is the rockwork is fixed in place, but one worries a bit. Should one?