Robert wrote, in part, in separate postings: : << do not like using sand for a number of reasons. It is often very alkaline, and it compacts. >> << I was referring to regular silica sand. >> Am I taking this out of context? Isn't silica inert? I use #2 - #3 "quartz" (so labeled, but it isn't really) sandblasting gravel and it doesn't dissolve as far as I can see. Bill