Biggen
Aquarium Advice Addict
I will second the use of a Diatom filter. You will have sparkling water in no time with it. I followed the exact instructions of that link that Timbo2 provided. I had no idea that my Magnum 350 was so versatile.
it seems that leaving the carbon in a tank for to long can leach phosphates into the tank.
This tank is the MOST clear out of all of my tanks AND I never change the media more than every 4-6 months.