Hello! Yes, as the post above says, Google is your friend. Here are some of the biggest reasons:
1) This is by far the biggest reason: It causes impaction. Bearded dragons are clumsy eaters, and many a time they will come back up with a mouthful of sand instead of food. Calcium sand (or Calci-Sand) is the worst, because when a bearded dragon fells like it needs more calcium, especially gravid females, it will eat the sand, causing impaction. It also neutralizes stomach acids, just like eating a whole thing of TUMS would for us. Another bad thing is it hardens up like cement in their stomachs.
2) It can stain them. Yes, quite literally. The pretty, colorful sand in pet stores can permanently stain bearded dragons bodies. Although I am not sure is directly harmful, I am sure it is not positive in any way.
3) It is a pain to clean and can host bad bacteria. Unlike a non-partical substate (tile, reptile carpet, shelf liner, etc) that you can just wipe down and sanitize, sand must be scooped up, and there isn't really a way to make sure your getting everything out, so bacteria can grow much more easily.
4) It isn't really what they live in in the wild. Unlike the common misconception that bearded dragons live on rolling hills of sand like the Sahara, they actually live more on a mixture of hard packed dirt and sand. It is not loose like what we put in our terrariums.
You may want to add the (few) pros to having sand, like it allows them to dig; it looks more natural, and suggest better alternatives, like adding a dig/lay box, and adding natural looking slate tile.
Hope this helps you and good luck!
