The bubble test (you can use Vinegar as well) will only let you know if it's Calcium Carbonate based sand like Aragonite. If it doesn't bubble it's likely Quartz. This doesn't mean it's 'bad' sand just lets you know what it's made of. Good white quartz sand will look and function just as good as aragonite sand at a fraction of the cost. Usually Calcium Carbonate based sands run around $1/lb. This can get pretty hefty when you realize that large reef tanks need several hundred pounds of sand. Quartz sand is much cheaper something more in the neighborhood of $1/15lbs 50lb bags are readily available for under $4.
Another substrate that is rarely mentioned in the hobby, which I was just recently informed of is call 'Pulverized Limestone'. This product will be sold in the garden section of HD or Lowes, although I've had best luck with HD. As it turns out the expensive Aquarium sand Aragonite is actually just ground up limestone, which is Calcium Carbonate.
Aragonite = Calcium Carbonate = Limestone
The hardest part about using the Pulverized Limestone is finding a grade with the right consistency for aquarium use. Some of it is more along the lines of gravel, and some more along the lines of dust. You need to find that happy 'sandy' medium. I did this by just poking a little hole in the bags and feeling the limestone. You can tell pretty easily whether it's dust, gravel or just right.
The pulverized limestone runs about the same price as Quartz sand @ $4/50lb bag.
I recently added the pulverized limestone to two of my prop tanks and it will be added to three more over the next couple of weeks. When looking at the limestone you should look for several characteristics. Color (you don't want brown sand), Consistency (sandy, not dusty or chunky) and price.
My local home depot did not have the right consistency but on a trip to atlanta a couple weeks back I found the right stuff. I bought several bags of it and wound up saving several hundred dollars over Aragonite aquarium sand.
