I use play sand form home depot and have'nt had any problems. I give it a good rinsing to get the dust and loose particles out. I've seen a lot of people use pool filter sand too and say they have great results.
Silca based sand shouldn't be a problem. It's only down side is that it won't help buffer the water levels like natural sand. Some people think it will leech silica into the water but that's an un-founded and non-proven myth.
I went to my LFS and they told me I shouln't use sand because the rays will eat it and die. They also told me sand should only be used with saltwater stingrays. They said I should use fine gravel. What do you think?