If I'm not mistaken, the calci-sand is claimed to be digestible, and if it isn't, its fine enough that small amounts should be able to pass through them when they reach a certain size. I've seen a lot of pictures of setups that successfully maintain leos and many have used sand or similar loose substrate. I'm not sure where you are getting your information on sand being an absolute no. The Leopard Gecko Manual says sand can be used for substrate for adult leopard geckoes. I'm wondering where you read or heard this.

PS. I didnt take the first response as being rude in any way.....not sure where the "rude" tone was....