can you use it as a substrate?
yes
can you use it for a DSB?
no
the sand is a silica sand (glass) it is theorized that with this type sand you might as well use crushed coral. The particle size is too large and the ed will harden and the sand will not disolve. it will just be there. The particle size is also not suitible for bacterial colonies.
The reason Southdown sand works is it is the right type of sand. Quickrete is not the right type of sand. If you want a sucessful tank, I would suggest making sure the sand is aragonite. Aragonite does a LOT more than buffer pH. It replenishes trace elements, calcuim, and ensures a healthy tank.
I would hate to see you save $100 now, just to loose $1000 when your tank crashes later down the road due to a bad decision. Please, if your going to be cheap, do it right. If you need help getting cheap aragonite, e-mail me and i can give you pointers. see my profile.
[ November 14, 2001: Message edited by: @knight ]