[Travis L. Stevens]

I prefer aragonite but see nothing wrong with silica sands.

Agreed. Now, with that said, I have my doubts that the silica in the sand (SiO2) and the glass of our tanks (~70%+ SiO2) is completely inert in saltwater. But, when and if glass/quartz releases any usable silicates, it will readily be taken up by other lifeforms, most likely without the aquarist ever noticing. Now, I contribute the original blooms of any algaes (micro, macro, diatom, etc) to the purity of the sand itself. Often "play sand" (and even aragonite or crushed limestone) is pretty nasty and dirty, and the nutrients and other chemicals that are in it can quickly be taken up by lifeforms and visually seen by the aquarist as a "bloom". Once all this stuff is taken up, you'll rarely see any blooms again.