Ohhh, they are so pretty!
At first I can't find chicken grit too, then I saw them at our local Ace Hardware Store. When I did not have chicken grit before I use either pumice, kanuma or akadama, or sometimes if I get those little crushed lava rock. But I prefer chicken grit now, the one that is insoluble crushed granite.
These are my remaining ones:
I have been experimenting where else to keep them cool, seems to like being beside a rock:
