sand impaction how big of threat is it?

[Nicky]

I"m hoping to purchase a beutiful fire red bearded dragon at my cousins pet store where the animals r kept pretty well anyways i have no idea what bedding to use i thought sand because they live in the desert but then there sand impaction is that a major problem for beardies? i wouldn;t know because ive never had one but what about you guys what kind of substraste do you use? and if its sand has it ever caused any problems?