I have to disagree. Washed and sifter play sand is fine for adult Bearded Dragons. Ask most Beardie experts, 75% will say go for it. As long as you feed outside the enclosure and take proper precautions that is .

I mean the best substrate, with the least risk is of course, paper towels or unprinted paper, but play sand is acceptable for adults.

IMO, you should never you use play sand for juveniles or baby Bearded Dragons.

If you do decide to use washed and sifter play sand, I'd like to make the suggestion of changing the substrate once a month or so. It brings down the risk for the spread of bacteria, etc.

Here is my little 4 month old, Yoda. He is a Hypo Tangerine.