When you buy your sand go to Lowe's or similar store that stocks it on shelves INSIDE the store. This should guarantee that it is dry. Buy the fine grade. A couple of weeks ago I got some like this at Lowe's to fill a new pair of Dynaudio Stand 4's. It worked great.
Sand and shot?
This question is really for what most bookshelf speakers sit on--the stand. I'm planning on filling a set of stands(24") but just have the sand presently. Do I really need lead shot as well or will the sand be enough. Most reviews I read on speakers mention stands with both. Any help would be most appreciated.