Let me start out by saying: Please, stay away from the ground English Walnut shells that looks like gravel. It's been widely known to cause severe impaction. I just lost a 16-inch sub-adult female that was kept on it before I got her and there were no signs of impaction until a day or two after I got her. I'm out nearly $300 in vet bills and cost of dragon, plus the sorrow and anguish I went through.
ESU makes some of this labled as "Desert Blend - Lizard Litter (Ground English Walnut Shells)." I don't know if any other company produces it or not.
Check this out: (WARNING!!! These photos are graphic and heartbreaking) mrskingsbioweb.com/beardeddragngrossanatomy.htm
* Photos of the autopsy I performed on the female beardie that died on me are at the bottom of this post.
I've been using the 50-pound bags of children's playsand for my oldest beardie ever since it was about 14-inches long and haven't had any problems. I guess its been about 4 months since I started using it.
I like it because its fine-particled but not dusty, easy to spot clean and looks nice. My beardie seems to like it, too.
Good, clean, rich, dirt that's reddish-brown in color is more like their natural environment, in most places they inhabit. I've been thinking of switching my beardie to dirt but I've changed my mind. However, dirt has finer particles than playsand and is probably the least troublesome "natural" substrate available.
I found some really good dirt and swapped my Savannah Monitor's Aspen bedding with it. My Sav LOVES it. However, he looks just like a lil', filthy, rotten piglet. Dirtier than I don't know what. I handle my beardie more than I do my Sav so I don't want to get myself or my house filthy every time I handle it.
I believe that the main factor in impaction is the bearded dragon, itself. Some are better aims with their tongue, getting less substrate with their prey/food, AND, some are more inquisitive than others, continuously testing their surroundings, thereby ingesting substrate. Its up to us to lessen the odds as much as possible.
Bottom line: I say either playsand or a good dirt mix.
* Here are some pics I took of my beardie that died from walnut shell impaction, even though we (Qualified Vet, and, myself, under Vet's directions.) tried oral treatments and enemas.
Here in this first pic you can see the walnut shells coming out from an incission in the lower part of the belly.

In this second pic you can see walnut shells in the lower part of the stomach and cricket remains in the upper part. She was so impacted that she couldn't digest the crickets. And she hadn't eaten ANYTHING in almost 2 weeks prior to her death.

Here in this third & final pic you can see the size of the different piles. The larger pile is undeigested crickets. The smaller pile is walnut shells. It's also important to note that the first few enemas produced a pile of walnut shells about the equivalent of a tablespoon or two.

Take care!
HH
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