Does that tank have overflows. When experimenting with my 1 1/2in. overflows on my 225, I found a large ph difference between running sumpless or running the large overflows. Even with my skimmer & scrubber running direct from the tank.  
 
  That would be an interesting measure. 
		
	
		
		
		
		
			
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				Doug
			 
		
		
		
		
	
		
		
	
	
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