I second that James. Dividers help bubbles rise out of the water, hopefully before they reach your return pump and get shot into the display tank. If you dont have a seperate refugium tank, then you also need dividers to attempt to keep sand, rock, macroalgae, etc. out of your return pump as these things would damage it. You also would want to have your protein skimmer (and its pumps) seperate from the sand, etc. as well, for the same reason.
If possible it is nice to have a seperate refugium and sump.
You would have a deep sand bed and macroalgae in your refugium with a light running over it 24 hours/ day. This helps naturally remove and process waste accumulation in your tank. Which in turn, helps control things like hair algae problems. It is also a safe place for reef bugs and worms to grow and multiply. These critters also help clean tank water as well as provide a food source for may fish and invertebrates.
You would have your heater, protien skimmer, bubble reducing baffles (optional), auto water top-off (optional) and return pump in the sump. This is where all of the mechanical processing of the water occurs.
Also, having either of these or both increases the volume of water in your system. This is beneficial in the sense that things change more slowly in a larger volume of water. Temperature changes more slowly, waste builds up more slowly, etc. Stability is what makes larger systems easier to maintain and healthier for tank inhabitants. Sumps and refugiums add volume and stability to out main tanks, as well as aid in filtration.
Hope this helps
Good Luck
-Christine
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)