Can one over-filter?

Zoom, yes this is what I was getting at. However, the higher the flowrate the more oxygen is delivered to the bacteria. Not less. And rather have a filter section thats bigger than the population than smaller, the trick is to match the flowrate and the surface area of filter media to create optimal settings. That being said, if both were higher than what was needed they would make No difference to the actual filtration.

 

So if the bacteria is that dependent on the oxygen, you could easily have a very low flow rate and just put an air curtain under your filtration media in the sump? I don't know why people don't already do that as backup for when the power goes out, it seems like the logical solution.