Velvet is 6 weeks.   
 
I do not like to treat anything with copper (poison) unless I absolutely have to.   
 
I have found that if you quarantine a fish in a separate tank with a biological filter (low stress) you can watch closely for anything to happen. 9 times out of 10 nothing does.  I always do this before I put a fish into my main display. 
 
Some have had success with no quarantine but I have lost a lot of fish over the past 30 years and 2 times completely lost every fish in my tank. 
		
	
		
		
		
		
		
	
		
		
	
	
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