Ok FR, I mixed eco-earth and play sand.

http://i1261.photobucket.com/albums/ii600/poison619/DSC01874_zps6e4a8fe0.jpg

http://i1261.photobucket.com/albums/ii600/poison619/DSC01873_zps102b9451.jpg

http://i1261.photobucket.com/albums/ii600/poison619/DSC01882_zps34fcd1d8.jpg

I would really like to go out and dig up similar substrate like in your pic but I don't think I've ever seen that type out here in San Diego. Most is hard packed.