Almost all commercial sand is silicate.  Silicates grow diatoms. Diatoms are ugly.  Therefore, don't use silicate sand in a reef aquarium.  I'd also worry about what else was in "commercial grade" sandbox sand.  Tons of things that wouldn't worry a kid will be bad for a reef. 
		
	
		
		
		
		
		
	
		
		
	
	
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