I use play sand from Home Depot in my tanks. It was like $3.50 for a 50lb bag. If you use it make sure you wash it A LOT before putting in your tank. With the play sand I filled up a bucket half way with sand and continued rinsing it till the water was clear. It probably took at least 20 fill ups and rinses to get it clear. From what I have read the silica sand is much cleaner out of the bag.
I used playground sand from home depot. The 50LB bag was 3$. I didn't know you were supposed to wash it, but now a few months later the fish are still doing okay. The only fish that died from unknown causes in that tank was an indian glassfish. But he was in it for over a month before he died.
I have used the play sand. But this last time I decided to use pool filter sand. And I will not go back to play sand. It didnt take as long to clean and the fish cant kick it up as easy. It floats just alittle then sinks right back down. I got it for about $7 for a 50lb bag.