My tank has been established for over a year now, I ran carbon last week after fighting red flatworms and lost some prized tankmates (my yellow tang & flame angel). I didn't understand carbon at the time, I ran a carbon filter from my freshwater days that hangs on the back. It didn't help much. After that, I read up a little on it. I ended up going simple, I took all the old carbon filters from my freshwater days (some were new leftovers), stripped out the carbon, ground it up, placed it in an old sock, and rinsed it well. (I was doubting it would do anything anyway...except maybe harmful stuff) Anyway, I placed sock with the pulverized carbon in the water, over the tube that empties into my refugium. I was amazed at the results the following day, my water was crystal clear ! I will now run it for 24 hours every 3-4 weeks going forward. It was easy to see the difference.