If you go to Wet Web Media, they talk alot of play sand, and southdown. Southdown, has been bought out two or three times. You have to look it up by the ICU number, or something like that. That is the only way. When it comes to silica sand versus calcium carbonate, the only real issue is buffering. They have debunked the silica leaching into systems fueling drastic amounts of algae. There is one WWM doctor that has a 300+gallon system that has 200lbs of silica based play sand and 100 lbs of live sand to seed. 4 years later (or something around that) no issue. The buffering capabilities are still under speculation. Some say it does some say it doesn't. The biggest issue with play sand is contaminates, and texture. Some silica based sand is jagged and can cut your sand sifters. Some is however, tumbled and nice and soft. Sorry, I have done a lot of research on this. When it comes to sand though, do not use "sand blasting sand". I know here in Savannah, we have a company that sells and delivers several different grades of masonry sand, and shell, and gravel. If you have a company such as this locally, I would check them out. Their per pound price should be great, and they will have different grades and colors of sand to choose from. If you are worried about silicates, take a bottle of vinegar and a cup. Sprinkle a little of the sand in the vinegar, if it bubbles its calcium, of not you are dealing with silica.
