On my 120 I run two xp3s, a mag 350, and an aquaclear 110. No carbon and crystal clear water. I'm not saying carbon doesn't do the job, I just don't use it. I remember a post that basicly broke it down to: Carbon quickly looses its chemical filtration properties and becomes a mechanical and biological filter within 48 to 72 hours. I think it becomes too expensive to keep replacing it so I just go with bio max and matrix. Its alot cheaper and does a good job. If you can afford to keep replacing the carbon than great but there is cheaper alternatives that don't compromise you water quality.