Sorry to hear.... 
 
 
But to answer your question..  1.5 gallons (containers) of LSM.  With a recirculation flow rate slighly lower than yours with the Mag 2.  (this is where I believe your problem lies, but that's just my opinion)  If you lowered your recirculation flow I think you would get closer to where you want to be.  With a high recirculation flow I think you are getting oxygen present through your entire reactor.  This is somewhat proven by your zero nitrate reading once your input was cut off. 
 
I would be tempted to swap out that Mag 2 for a ehiem 1048 or something similar.  Trust me, the results of lower nitrate are quite nice, as I have corals growing again that had stops for many months.  It's made me a believer... so far. 
		
	
		
		
		
		
		
	
		
		
	
	
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