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

[mr.wilson]

Originally Posted by banditpowdercoat

Then by your own words, is NOT a FIFO. can not have extra, or recirculating water for a FIFO style sump

For a FIFO, All water that enters sump, needs to pass through the skimmer ONCE, then on through the rest of the system ONCE, then back to tank. NO bypass, and no water recircing in loops. Everything is in series.

I agree that the most efficient skimmer feeding system is a direct feed from the display drain, but most protein skimmers are built by manufacturers to cut production costs, so they use a one pump does all system.

If you are directly feeding a recirculating skimmer from a drain, you should always have an emergency bypass T or Y in the event that the skimmer clogs, can't keep up with the sump return pump, or a surge of water in the tank while you are servicing it. In the event that any water takes the T or Y, the system is no longer FIFO or 100% efficient as MrOm would say

With a little valve tweaking you can get close enough to a perfect match with the sump & skimmer pumps to call it "efficient". The good thing about directing the skimmer effluent over a glass partition and trying to match the pump outputs is if you don't get a perfect match, the system is se;f regulating, in that you don't have a skimmer zone that runs dry when the skimmer pump outcompetes, or an overflowing skimmer if the return pump outcompetes.