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

[mr.wilson]

The question on the table isn't the limitations of protein skimmers, it's simply how much water do we need to feed them. I really don't see how anyone can argue that their protein skimmer that processes 500 GPH needs 1000 GPH fed to it. After you move beyond that no brainer you figure out a way of making sure that all of the water you run through the sump goes through the protein skimmer and does so only once. That's maximum efficiency.