HELP!My Aloe vera pups are dying!

[Collext]

what they sell as "paver sand" in all the big box stores works fine. Gravel is sold in pet shops for aquariums. You could use at least partly potting mix for cactus.

"The worst possible choice is "Joint Lock" or "Paver" sand which is sold to inexperienced "Do-it-your-selfers" as a leveling medium and bed for brick work. This sand is "Polymer modified," which means that it contains an additive that will harden when it gets wet. "
I found this on the internet?

[applestar]

Look at the package instructions. The kind you are talking about will say something like sweep into gaps between pavers/bricks then spray with water to set. You could also test by putting some in a cup and adding a bit of water.

All purpose sand should be fine.
I've used underlayment gravel/pebble mix for pavers as well as untreated gravel/sand mix for filling between pavers. If in doubt or if you want especially "clean" substrate, you can also rinse the sand/gravel before using. All kinds of stuff float and sink out of them.