If you truly want a tank that close to the floor, use a simple frame of 1 x 8 lumber on edge with a 3/4 inch plywood top. It will be rock solid without the roughness of the cinder block approach. It can also be stained or painted to suit your tastes.
I always build my own stands and must warn you that very short stands cause maintenance problems. You can't even drain the tank properly into a bucket when the tank is sitting too low.

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Fishless cycling