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

[banditpowdercoat]

Mr Wilson. If you were to use a single pass skimmer for a FIFO, how would you guarantee that the sump return pump equaled EXACTLY what the skimmer inlet pump was pushing? To be true FIFO, all the water from the tank drain needs to pass through the skimmer, just once. Then, the return pump pumps the skimmed water back to the tank. it would be next to impossible to match them exactly. Thats why a recirc would work better. A recirc doesnt care what goes into it for flow to make the bubbles etc. The slower the inlet flow, the longer the contact time the water has, because bubble production remains constant.