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

[danny zubot]

I was with you up until this post, and that's mostly because I was having trouble understanding both sides until now. However, a tank + sump is a closed system. The amount of water running through the sump should be irrelevant. It would be the same as a HOB skimmer running in a sumpless tank with 100x turnover using just powerheads. In this case, the DT is just like a big sump (since there is no sump).

Water in the sump is the same water as the DT. There is no special separation between the two except the OF, a pump, and some pipe.

The concept that "a sump is not a filter" is a good one. A sump really is nothing except a place to store equipment.

Now if your argument is that a low-flow overflow extracts surfactants better, perhaps you can discuss that more.

That's what I said only in different words. Not to kick a dead horse, but the skimmer controls its own rate of flow through the body of the skimmer. In which case slower is better for extracting surfactants, but only within the skimmer itself. The higher the contact time between the water and the bubbles, the more effective the skimmer is at pulling out waste. This has nothing to do with the rate of flow through the sump, tank, fuge etc.