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					Originally Posted by reef_raf
					
				 
				Bob, I believe O2 goes in by itself quite easily once CO2 is dispelled. The skimmer does an excellent job of agitating the water that flows through it, and I believe this does in fact provide for a higher O2 level than if a skimmer was not used. 
Good ciculation in a tank with the sufficient surface agitation could provide the same amount of CO2 off-gassing, but this would require a lot of water movement. 
Ultimately there is a maximum and saying that a skimmed tank will always be higher in O2 is certainly not true. A skimmer will not supersaturate O2 in to solution. It does provide an easy way to remove CO2 though.  
So, required? No. Helpful in this task? I believe so. Again, so supporting research, but the logic is sound. 
			
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I agree with you Brad.  You would need a lot of surface agitation like running a powerhead with a venturi device.  Unfortunately, to get that agitation would mean a lot of salt all around my tank.  The skimmer does that for me without the salt spray.  If I turn off my skimmer now and just leave the powerheads on (with lots of surface ripples), I can almost guarantee the death of some of my fish (not all) within a month.  Should I try it as an experiment and see if I can reproduce the same result as I did last time?