That Kole looks great! Nice to see him in the DT.  
Not sure if you feed him any seaweed but I have one in my tank and also a starry blenny and I notice a marked increase in aggression in the Kole tang when I don't feed Nori on a clip every couple days. Once I put the clip in there they'll eat side by side and not fight anymore, it's really weird. 
		
	
		
		
		
		
		
	
		
		
	
	
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