I guess on average about 2x, 3x per week.  Not very often (sometimes I'll let it go as long as a week, as long as I can still see into the tank).  Basically it depends on how ambitious I feel! 
 
I notice that each tank has very different schedules.  One tank can't go for more than a day or two before it's too opaque and the other can go as long as two weeks before it gets comparable to the other tank at two days. 
		
	
		
		
		
		
			
				__________________ 
				 -- Tony 
 My next hobby will be flooding my basement while repeatedly banging my head against a brick wall and tearing up $100 bills.  Whee! 
 
			 
		
		
		
		
	
		
		
	
	
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