pool filter sand would be your best bet. i have AquaQuartz in my 37 gallon tank, and it is an off-white, more natural than the bleach white sand you get at the LFS that literally looks and has the consistency of flour.
Quickrete can be used, but the AquaQuartz that i used was nearly clean and took about 30 seconds to clean fully, rather than the long time it will take to get play sand or quickrete clean.
Quickrete can be used, but the AquaQuartz that i used was nearly clean and took about 30 seconds to clean fully, rather than the long time it will take to get play sand or quickrete clean.