The carbons, as mentioned, will be exhausted probably within a week, depending onthe amount used. It can be used as a source of biomedia but eventually all the little hoes that make it have some much surface area get filled with dead bacteria and then it is no better or worse than using aquarium gravel. It won't hurt to use the carbon, but if you are truely using it to keep the tank clean then buy freshstuff every week. And only plants or water changes will deal with nitrates. The only bacteria that eats nitrates is anerobic.
Ever wonder why the brita filters switched from a little sticker to tell you when to change the filter to a runnign switch that measure pass through?
Ever wonder why the brita filters switched from a little sticker to tell you when to change the filter to a runnign switch that measure pass through?
I've just come back to this great hobby after a ten year absence due to my 6x2x2 tank crash, the stand collapsed nearly killing my wife & I 
Understandably this disheartened me very much, I lost everything fish, tank, Eheims, the lot!!! It took almost 2 weeks working from sun up, to bed time to clean our home up ... I was destroyed after this & I was never returning until my family (bless them all) all clubbed together on my 46th birthday (August-04) & brought me a 6'Lx2'Wx27"H with everything ... I'm so happy now, but you can see how my old school views on carbon has suffered due to my 10 year absence ..... I can see the new ways now thanks very much all & I am taking my carbon out & using it only when needed ... I used to boil carbon in a saucepan for 20mins in water to recharge it, an old trick I learned!