Nosmada,
How is your refugium a "hang-on"?? If that is a hang-on, you must have a BIG tank!
btw, what are your 3rd and 4th chambers going to have in them?
Ca2,
I'm sticking with what Mr. Salty says on this one. Also, I'm not going to control the water flow in from the overflow....yes, gravity return is easier and less of a hassle, but I want to have a sump with a refugium section down below with skimmer, all in one kind of thing. My main desire is to reduce trates with caulerpa...and I wouldn't like the way the above tank would look in my living room.
Re: death by impellers...Funny, my lfs has had my same setup for a few years and I really like seeing how much life flows through the pump and out the return!