Beignet said:... I've read quite a bit about the flow rates through the tank and sump and my understanding is that a turnover rate of about 3X/hour is all you need. This is advantageous for extending contact time with the skimmer and any other sump filtration (so I've read). ...
Just as a fun discussion point :
I have read in several places that also, but it does not really make sense to me from a physics standpoint.
Contact time INSIDE the skimmer, dwell time contact with the bubbles themselves, is certainly important.
But beyond that, it seems that you are over-cleaning the sump water.
Basically, the higher the contaminant level, the more efficient your filter should be at removal.
Especially for carbon or other chemical filtration.
So getting the sump water cleaner than the main tank should make filtration less efficient, not more.
Thus the more flow between sump and main tank the better.
However, there is certainly a point of diminishing returns.
And there is the cost/hassle of all the flow.
So 3X might be a good practical tradeoff point. I think I have about 5X is all.
I just don't think it is "better" than a higher rate.