The issue of substrates have often been debated here. You pretty much have to decide which one works the best for you. Some go for washed playsand as it has a more natural appearance (I don't see why, as bearded dragons don't live in deserts, mostly arid areas with hard packed sand, not lose 'beach' like sand). Others say keeping the dragon on paper towel or newspaper is better because there is no chance the dragon will eat it. Other similar substrates are non-stick shelf liner (Duck Brand, the non porous kind). I have used plastic tablecloth with excellent results (I bought a 3'x100' roll on sale, spot clean daily, replace completely every month or so)
Pretty much everybody agrees that petstore bought products are a nono, either causing a high risk of impaction, choking or allow for bacterial and mold to grow. These include any 'calcium' based sands, crushed walnut shells, bark mulch or shavings etc.
To summarize, the best choices for an adult dragon (and for babies, excluding sand) is: non-stick shelf liner, papertowel, newsprint, plastic tablecloth, non-porous tiles or washed playsand.
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PHLdyPayne