Not all sand is equal, some will mess with pH. As far as argonite is concerned, the bag my sand came in is not marked. All I know is people on the FW
side of this board like the Playsand found at Home Depot. It has different names, depending on where you are in the country. The stuff I found was called Target Playsand and was actually recommended by my favorite LFS
guy. He said one 50 lb bag would be around $5 and it would have more sand in it than I would know what to do with. And he was right!!