24 hours for strength, but you can get it wet as soon as it skins over. If it isn't dry enough though, it can leach acetic cid into the water. I did this once and al my fish jumped out of the tank. 
Waiting 24 hours isn't so bad... 
		
	
		
		
		
		
			
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				Brad
			 
		
		
		
		
	
		
		
	
	
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