Join Date: Mar 2011
Location: Oregon State Beavers!
The thing about carbon is that it only absorbs stuff for roughly 2-4 weeks, depending on your bio-load and the filter size. So after that time period you aren't using carbon for what it is intended, but rather as a source of surface ara for beneficial bacteria. Now that isn't bad, but personally I feel that using carbon for extended periods of time causes more clogging than if I was using actually bio-media.
Carbon is good for removing odors and coloring that can occur with driftwood, peat moss, etc. If you choose to not use carbon (I have seven tanks all without carbon) then it would be advisable to make sure you stay on your water changes as that is going to be the main way you remove odors and any coloration.
Carbon is good for what it is intended, it only sucks having to refill/buy the extra carbon so frequently. I personally don't know for sure about it absorbing beneficial nutrients, but I think there is enough people who run fully planted tanks alongside carbon with great success to prove that false.