I'm using an iwaki 40rxt going into 2 sea swirls for the closed loop on my 100 gal. i also have a quiet one, and tried it out on the closed loop, but I was looking for more flow. I'm using the quiet one on my skimmer; it works well but runs pretty hot. I'm pretty sure that either the quiet one puts out less than 1100 gph in any actual application, or the iwaki puts way more out than it's 1250gph rating (approximately) because I found a really big increase in flow going to the iwaki.