how many times a hour should the water go through the sump?

[mark]

There might be an ideal turnover rate if the skimmers were 100% efficient but doubt they're close. Even if they were, what's the big deal if one decides to have the return pump contribute to the overall turnover of the tank. Really, if one could accurately measure waste remove by our little hobby skimmers, would there be a significant difference between 1x, 2x, 5x flow through?