First, all my leopard geckos are on paper towels and I haven't used the following method myself, but it has been recommended to me and posted on this board a couple of times. I don't remember who first suggested it, so if that person is reading this please post your name so I can give you due credit!
Try this in a small amound before doing the whole 200 lbs!
When you add water to sand and it then dries out, it hardens and holds shapes such as hills and valleys. The sand becomes hard and is no longer acts as individual grains (except for a light scattering of loose sand granules in some places). Leos can dig in it and it's not supposed to collapse.
I've also heard of a blend of sand, peat moss, and clay kitty litter.
Proexotics has posted some information about the substrate they use for monitors and uromastics. That substrate is not so much moldeable as burrowable, if that's a word.
Please test any of the above yourself before letting your leos find out about its reliability!
Also, if you keep plants in their pots but apply a light layer of the substrate on top, the plants do better and still look natural.
Last thought: keep calcium and/or minerall in there at all times. Well supplemented leos seem less likely to deliberately lick sand repeatedly.
Let us know what you decide and how it goes, if you would. I am writing this assuming you are talking about adult leos. Young ones are in much more danger of impaction on sand.
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Andrea A. 