+1 for giving him more time in quarantine.  Once you're happy you've avoided parasites I wouldn't bother with the tank swaps, just give him/her a quiet place to hangout and have a chance to recover.  The other fish in the display might bully it enough to push it the wrong way over the edge. 
		
	
		
		
		
		
		
	
		
		
	
	
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