We don't really over rate them, the catalog and manual explain the rating system, the highest or stated rating is for a FOWLR or what used to be called a Dutch Reef, basically a bunch of caulerpas and mushrooms and a few leathers. Deduct 20% for a soft coral tank, 40% for LPS or mixed reef, 60% for SPS and 70% for a very heavily stocked SPS and fish tank. The ratings reflect a desire to stay consistent with our ratings from the earliest days, we have made skimmers since the 60s and at that time through the 80's the dutch or non photosynthetic reef was what people kept because the lighting technology and knowledge on calcium demand, etc was just not available. If you look at an older Baensch Marine Atlas or find an old FAMA from the 80's or early 90s you can see what was the vogue at the time, a huge bank of T-12 flourescents and a few leathers, caulerpas and mushrooms. Maybe some flame scallops or a sea apple and a very few fish.