Old Castle Paver's Sand? Right or Wrong

I'd go with live sand. you can buy it at any LFS that sell marine stuff.

Yes, you can use that sand. Of, at Lowes or Home Depot, search for Quickcrete Med. grain white sand. It's $3 for a 50lb bag and works perfectly.

Live sand is nice, yeah...but also expensive. Get the sand from Home Depot/Lowes and then go and get 2lb. - 3lb. of live sand and mix it. Soon all of your sand will be "live sand".