I did a grip of research on refugiums when i made my sump and i decided to put my return in the middle and my refugium at one of the other sides. the reason i did this is that everything i was reading states that refugium should get under 300gl of flow to be more effective at removing waste like nitrates and phosfates. sa currently my refugium gets about 180 to 200 gl of flow while my sump and skimmer side get about 350 to 400 gl flow rate per hour.