In my 90 I have quickcrete. It was play sand from the pacific washed, and sterilized. I checked into it and they use a autoclave for sterilization. It is about as pure as sand can get. The draw back is the darker color, so I use it as a base, and put live aragonite sand over the top of it. It got all mixed together over time and has a realy cool speckled effects. If somebody knows of chemicals in it I would love to hear what they are, and what they are basing it on.