You don't have to limit yourself to media you can buy in the pet stores.
Check out this link on all different kinds of biomedia and their effectiveness.
http://www.monsterfishkeepers.com/forum ... hp?t=88677
In mine, I've got fluval prefilter (which doesn't really work), a green scrubbie for coarse filtration, carbon (I buy loose carbon, and bag it myself, much cheaper), bioballs, and biomax.
Also, you might get lucky in your local classifieds too. I found 4 small bottles of loose carbon, the bioballs, and a media bag for $20 in the classifieds.