When i started a new tank and used live rock and live sand i never really had an "ammonia spike" it was a very small almost un noticeable cycle.  I would think the nitrate and nitrites are from the shrimp and clams you added to your tank.  I could be wrong but that is my experience with it. A week after setting it up i had all my fish and coral in my tank with no issues. 
		
	
		
		
		
		
		
	
		
		
	
	
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