The idea of a sump is a place to put some equipment, protien skimmer with its pump, a heater, and your return pump which is either internal/submersible or external. A good deal of oxygenation goes on in the sump. You can also place carbon or phosphate removers in there.
There are many ways to work a refugium as I am learning right now. You can have macro algea's for nutrient export, a DSB for biological filtration, as well as live rock for further filtration, you can use it to grow pods and snails where there are no preditors to eat them.
Most of your water can go through the sump and be processed by your machanical filtration, some water is also diverted to the refugium for biological filtration and then back to the sump for skimmer and then back to the main display.
If you are going to have a reef tank then there is not need to use a UV sterilizer or Ozone as they might cause more harm than good depending on the system you want.
Right now I have a 90 gallon display, most of the water is going to my wet/dry which has a skimmer/pump, heater, and has an external pump for return to the main. Part of the water from the main is going to my 55 gallon refugium via gravity feed. This gravity fed water is going much slower so that the DSB and Chaetomorphia algae that I have can process the water by means of biological filtration.
O2 gets introduce by the rushing water into the sump, in the case of a wet/dry the bio balls are adding O2 by splitting the water over and over. The skimmer adds alot of the O2 via foam fractioning. The Ozonizer adds O3 which can kill benifical plankton, pod larvae, worms and other organisums. I've used ozone before but am not convinced it was doing my system justice overall, there are pros and cons and I think the cons outweigh the pros.
Thomas
