All tangs are prone to Ich so it is important to quarentine - not only Tangs but any new fish you plan on introducing to your display.  IMO the 2 Tangs that are the "most" prone to Ich are the Powder Blue and the Achilles.  I really really wanted an Achilles when I set up my 190 but between not being able to find a healthy one and the almost guarantee of Ich I went with a Blonde Naso instead.  I have a Yellow and and Regal/Hippo in my 230 and - knocking furiosly on wooden head - I have never experienced Ich on any of them. 
		
	
		
		
		
		
		
	
		
		
	
	
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