you'd probably get a better answer on one of those forums then since most here deal with frogs. I'm not saying no one here has ever used sand but i'm willing to bet there's more that don't than due. If you're building a viv for some crabs you're better off getting your information from the other forums you go to about crabs. Hence you haven't really got any answers from anyone but me here, as there's probably not many people here that deal with crabs.