If you use blasting sand, be aware that the grains are sharp. That means you will have problems trying to keep any fish that "chews" on the sand, like corys, for example. Those fish will damage their mouths usually resulting in death. I lost every fish I tried that "chew" the sand when I used black blasting grit, which is actually black slag. Soilmaster Pro Select Charcoal is almost black and very cheap, but it does not contain sharp particles, so my cory's are able to chew to their heart's content.