first off what is the size of your display tank...it is important..like fishgeek88 said the bigger the sump, the better..the size of the display will deterimine the minium size of your sump and the return pump that filters..
first off what is the size of your display tank...it is important..like fishgeek88 said the bigger the sump, the better..the size of the display will deterimine the minium size of your sump and the return pump that filters..
If I was to keep my skimmer in the sump, I like to keep the flow rate through it at or a bit above the flow rate through the skimmer. This way, you will optimize the amount of non filtered water to pass through the skimmer on its way through the sump.
For instance- I will be using a mag 5 for return and my skimmer pump is 500 gph, that will be in a 40 gallon breeder sump.
As far as minimum size, I usually map out the skimmer area, return area, and figure out how much room I need/want for the fuge and other misc. equipment. then go a bit bigger for future upgrades.
I have read that flow rate through a sump should be slow, to optimize contact time with filtration, but this can lead to detrius buildup and dead spots. I like to add some flow with water pumps/power heads in the sump instead of ramping up the flow rate through it.
Hope the info helps, but its just my opinion. There are so many different ways to go about sumps with pros and cons to each.