I've tried them three times and they have all disappeared within a week, with no ill effects.  In my tank they probably overate themselves.  Going to try one again soon, algea is coming back. 
		
	
		
		
		
		
			
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				Current tank:  120g 30g fuge 2x400w MH 220VHO
			 
		
		
		
		
	
		
		
	
	
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