I agree with kip about the silica playsand and the Warning about the dust. Here is a little tidbit from an article about changing substrate that I have been working on.
Very Generally speaking Silica sand, lets say industrial style is a high purity quartz (SiO2) sand. Silica is a stable compound and will not leach silicates into your tank for it has no "sillicates in it. Depending on its chemical and physical characteristics, silica sand is used as glass sand, foundry sand, abrasives ..etc. Silica sand can contain tiny amounts of impurities, such as iron, manganese, chromium, calcium, or aluminum, and give the sand its color depending on how much of these impurities are contained within. So it depends on geographically where your silica sand comes from as to how much impurities it contains. If you are going to use silica sand look for white silica sand as it is much more aesthetically pleasing
A warning about silica crystals:
Silicosis is a disabling, nonreversible and sometimes fatal lung disease caused by overexposure to respirable crystalline silica. More than one million U.S. workers are exposed to crystalline silica, and each year more than 250 die from silicosis. There is no cure for the disease, but it is 100 percent preventable if employers, workers, and health professionals work together to reduce exposures.
So in other words do not breath this dust. FYI there is also a warning lable required by the state of California that is required on silica play sand.
Thomas
