I am not too sure about it but I think mandarin have resistant to ICH , Velvet and other skin parasites duo to the special mucus  covering their skin. 
 I had mandarin for years, one time in a period of a week it completely went white! I was sure he is going back to the Creator, but few days later he became normal again. 
		
	
		
		
		
		
		
	
		
		
	
	
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