1) false (if the question means any and all) 
 
2) if I understand correctly, 2 part adds salt without the rest of the "stuff" in the salt bucket.  Adding only 2 part will reduce the ratio of the "stuff" in your tank, creating an imbalance.  Doing a 10% water change will only improve the imbalance 10%. 
		
	
		
		
		
		
		
	
		
			
			
			
			
			
			
			
			
			
				
			
			
		 
		
	
	
	 |