Technically a sump and a refugium are diffrent, A sump would be used for your return pump, skimmer, reactor, etc. A refugium is mainly for nutrient export, micro and macr fauna, a safe haven for fish or coral, taken from your DT, and pods. My fuge is custom made out of acrylic and has three sections, the water enters into section one where the skimmer lives, section two is the DSB and fauna, section three is where the return pump and fluidizer reactor live. There are many, many ways to configure a fuge. I noticed a big diffrence withn a couple of days, in a drop off in algae growth.