Nitrate and Ammo

[bullit67]

Well this sounds like a newbie ? but I have been at this for about 3 years or so now. but I have had a nitrate problem since day one I cant seem to get my nitrate down below 20PPM I am running a 72 Gal Bow front it is not over stocked only about 8 fish in total on my last water test I also have a little ammo 0.25PPM Ph is good and no nitrite. Any one have any ideas water changes dont help

any ideas would be great