Hey Steve,
I read your link the Randy's article, and I read the entire thing. At the end, he actually recommends ADDING silicate to our systems, shows how to do it, and where to buy it.
My point is that you seem to post that link as a reason not to use silica based sands, when it actually supports using silica sand over calcerous based sands, as a potential source of needed silica for our systems. Randy makes the point that organisms we want, like sponges, mollusks etc, actually need more silica than is what in our reef tak.