Carbon?

Hey Guys,
I need to know the pro's and con's with using activated carbon as a filter media. Many if not all of my clients do not use carbon what so ever in their tanks and I've been told by many aquarists that simply biological filtration is the best way to go. However, I see here on 3 reef that a lot of people use carbon in their set up's. I maintain 3 tanks. One of which is mine. The other two are held at the LFS where I work. Should I introduce carbon?

 

http://www.3reef.com/forums/general-reef-topics/carbon-57333.html

 

Thanks>