currently open top and loving it! downside is the evaporation and my hand being in the tank all the time these days since it's so easy. 
 
bought the 1/2" clear mesh from BRS for the 400 and never got around to making a cover. bought the 1/4" for my current tank and can't bring myself to cover it either lol. 
		
	
		
		
		
		
			
		
		
		
		
	
		
		
	
	
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