Southdown tropical play sand is highly recomended over any other type of sand. If you have access to it, use it. If you're like me and don't have access to it, you have to come up with alternatives. Here in the pacific northwest, we have silica sand. The only problem I've come across using this is it's sometimes hard to maintain the proper ph. Other than that, it works fine for me. The problem I have is people who have access to the southdown sand and don't use it. Good luck. COOP.