Hey leo, what about a false sand bed? I used some sand, along with a laquer resin. I used it inside my tank, and unfortunately it turned green, because it became live. I think if it is put on the outside of the tank, under the glass, it should stay white, and look like sand. We also have plasti-kote "stone touch" paint over here. It looks just like sand. Spraying that on the bottom outside could be an option too......
Either way, Im curious to see what you choose, should look nice either way =)