Firstly hi as I am new.
I have been reading some of the posts and the one about impaction of sand in a leopard gecko. Sand should never be used as a substrate and I always recommend fine grain Oyster shell.
Sand being a silicate does not break down in the digestive tract leading to impaction. I was reading an article recently and some people are warning about Calisand as there have been reports of this causing impaction.
Oyster shell being as the name says is ground up shell, pure calcium which your lizard can accidently as well as deliberately eat and should help to keep your pet lizard healthy so long as all the other enviromental factors are in place
Clive

I've been keeping mine on sand and they've always been fine. It's not like they eat sand. Some of it might get accidentally swallowed by not to the extent where its causing them any problems or discomfort.

Ideally they should be kept on stone anyway to mimic their natural habitat.

You could just go and get some stone tiles from your local B&Q or Homebase and cook them in your oven on 200C for about 25mins to disinfect them, wait for them to cool down and put them in the viv. Use sand to fill in the cracks in between the tiles so their lil toes don't get stuck in between.

There are several other reasons for using Oyster shell firstly it is abrasive and helps keep the toe nails to a reasonable level especially Uromastyx that seem to enjoy moving it around, Bearded and Madagascan spiny tails also like to dig in it.
It has larger granules than sand is relatively stable so rocks can be used to create a natural setup, but care must still be used to ensure stability.
This substrate is very absorbant which makes spot cleaning very easy.
In the good old days I used to put a small dish of ground up cuttle fish in all the vivs with gravid females for extra Calcium, then I put in a small dish of Oyster shell and the females did go to the bowls and eat it.
The natural progression would be to use it as a substrate I have observed all species eat it, and especially Uromastyx Geryii which I managed to breed last year.


Uromastyx Geryii, Occellata, Mali, Sudan.
Geckos Frog Eyed, Standings Day, Leopard, Fat Tailed. Chameleons High Casque, Hatchling Yemens Chameleons hatched 07/06 the eggs were laid last November, Madagascan Spiny Tails, Bearded dragons and Rankins. and a few snakes.