I used Quikrete 50 Lb. Play Sand from Lowes. But not by itself. I also added 40lbs live sand, and about 10lbs from another setup. It is doing wonderful, no problems and my soft shell crab loves it he won't come out of the sand. The 2 types of sand where different colors so if you don't mix it together then you will see a difference. Ours is mixed in and nobody knows the difference.
It didn't give us any problems at all the live sand caused more problems than the play sand. But everybody has a different opinion on this subject.