Since the only ETSS skimmers I've heard of are the downdraft skimmers, I'll assume that is what you are considering. I would be careful with these type skimmers, they are very efficient and can strip the water of some of the nutrients beneficial to our corals. For downdraft, I usually recommend getting one that is sized specifically for your size tank, where as with a standard venturi type skimmer, I recommend oversizing. FWIW, I have heard good things about ETSS skimmers in general.