I was at Home Depot looking for Southdown sand. No one has it. I did find this at the Home Depot in Bridgewater. It has this disclaimer on the package: "This product contains small amounts of crysalline silica (CAS 14808-60-7), A common mineral found in natural sand and stones......" Is this a problem? It is distributed by a company called Old Castle Retail. It did mention not for aquarium use. Anybody got a take on this stuff?