If you are going to dirt the tank...you need...well....dirt....soil of some type to use for the substrate with either small diameter gravel or sand on top of the dirt.....and if you go dirt/soil....you need to start out with enough of the right species of plants and have the correct lights-otherwise the tank can crash....
I have lots of information on the Natural planted dirt/soil based tanks here...
http://www.bettafish.com/showthread.php?t=84915
http://www.bettafish.com/album.php?u=17234
I have lots of information on the Natural planted dirt/soil based tanks here...
http://www.bettafish.com/showthread.php?t=84915
http://www.bettafish.com/album.php?u=17234