Beardies lick their environment all the time, adult and baby. I don't think there is ever time when you can use sand. Sand in a beardies tank gets poohed on and there is liquid with that pooh and scoop as you might, you will not get it all. Then the waste begins to break down and bacteria start to form leaving your sand littered with bacteria. It would be like living in a kitty litter pan. Since beardies lick their environment they take in the bacteria that can lead to infections and all kinds of problems not to mention it may cause them to be impacted. Regardless of what a few may say, whether it be dirt with bugs seeded into it, or sand..there is a terrible risk that I myself, am not willing to take and impaction and infection are two of those risks. Walnut shells, sand, dirt, topsoil, none of them in my opinion should ever be used. I don't want the risk to my beardies.