IMHO
the things you really need to worry about are minerals TOO, if it came from a quarry, or anything for construction,
Remember no bacteria or contaminants in construction is not the same as safe for a reef, be extrremely careful, if it is the stuff they use for concrete
it could have lye and metals in there, which you definitely do not want, personally I would be extremely careful using anything that I don't know the complete history and make up of
If you want a cheap alternative, get southdown play sand, it may be avail. at HOMEDEPOT in your area, if not Quikrete makes a quartz type sand, which i have heard works well for other people, and quartz would be safe, both are inexpensiveSD is @ $5+- for 50 lbs, but your best substrate is Aragonite(SD) based, it will help you with your other parameteres as well as your nitrate reduction
HTH
[ December 13, 2001: Message edited by: fshhub ]