GB,

The biggest difference is the silicates in the water will feed diatom
algea, the silica sand does not disolve so it does not feed diatom algea.

Kim
http://www.jensalt.com

George Burnt wrote:
If using tap water for a reef is a sin because it might contain silicates,
why is it ok to use silica based sand? Or I am I compaing apples to oranges
here.

GB