Was at Home Depot looking for play sand for the new tank. No luck - but.....
In the garden and lawn area they had 40 pound bags of granular dolamitic limestone for lawns. Looked at the ingredients - dolamitic limestone 90% dust free and thought - why not? This is the same stuff as sold in pet stores in crushed form. Looked at the texture - about the same as the sand in the LFS
I did a test run in a bucket - settled nicely - didn't clump, pH around 8.2 to 8.4.
At $2.99 a bag I'm going to give it a try.