I've been using Lapis Lustre Monterey beach sand about 2-3 years now. Fish love it and the price is right. $14 for 50lbs. I got mines from a local concrete store. #12 btw.
http://www.bestmaterials.com/detail.aspx?ID=18163
http://www.bestmaterials.com/detail.aspx?ID=18163