what can i put at the bottom of my fish tank?

[melindaheans]

i just got a new 20 gallon tank and i was wondering what i should put at the bottom, gravel or sand, which is cheaper...and is there something i can get that is natural that doesnt cost alot? Ever out of my back yard?

 

[smomus]

Sand doesn't cost much at all. Depending what kind you get can be just a couple bucks for 50lbs