I have used lemon juice in the stalks with good success...Leave the rock in the tank, if killing multiple heads only do a couple at once if you have a small tank, or your PH will swing!! 
		
	
		
		
		
		
			
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				500G Mixed Reef
   
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Electrician, Electronics Technician, I can help with any electrical questions you might have!! 
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Kevin
			  
		
		
		
		
	
		
		
	
	
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