I believe there is a place to put carbon in, or you could take out the bio balls, and run a carbon pack in its place.... Aquarium designs on Brookhollow and 281 has new ones on the shelf, cheap too (around $100)! Go by and look at it and see...... Having bioballs and live rock together is sort of redundant. No need for the balls if you have ample live rock to carryout the denitrification process, hence do away with the balls and replace with a carbon filter pack. Another choice would be the Prizm deluxe skimmer by Red Sea (also around $100 w/upgrade)..... The Deluxe version has a place for carbon filtration paks... ALTHOUGH, I have one of these on my 30g (w/o the deluxe upgrade-$25) and it doesnt pull that much skimmate, sorry to say, I would NOT recommend this brand. But if you want, I will sell you mine for $25, you can buy the upgrade for $25, and have what you need for $50...Done deal... PM me if your interested.... Good luck..Erick...