I think I'd be VERY concerned if I noticed the waterline location changing (ie. indicating settling). What is the floor the tank is sitting on? Ie. upstairs/downstairs, sitting on joists, parallel perpendicular etc etc. ? 
		
	
		
		
		
		
			
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				 -- 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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