How can you run a reef tank without using carbon ?

[Casey8]

reefwars, I am using r/o water. I will check my sump tomorrow, you maybe right the smell may come from there. I didn't clean my sump for awhile now. But it never happened like that before when I used carbon. Why did jagermaier and you mention about a skimmer, is it something to do with the skimmer too ? But I clean the cup everyday, because it skims too much of goo even I have dialed it to a dry skim, but still, I am afraid of getting overflow when I'm not home.