I've had a couple different ATS. I think every tank should have one. Besides the nitrate and phosphate removal they grow pods like crazy. My current system has a 210 gal refugium, an ATS, and no skimmer. A skimmer removes the waist before it is processed by your bacteria. An ATS removes the waist after your bacteria has precess it. One big difference between your ATS and refugium is that The ATS uses CO2 from the air, and your refugium uses CO2 from the water. More info than you probably wanted but thought it might Help.