At this point, I'd be suspicious of anything that's going into the tank; CO2, reactor media, food, carbon, supplements, salt, filter socks...  If I were fighting this fight, I'd take every one of those things offline, go buy small amounts new of all the things you need to add (ca, alk, food, salt).  Then I think I'd try one frag for a week or two -- something you can afford to lose -- and start adding the other stuff back in, one-a-week.  I really doubt it is the rock, glass or silicone (although that's a possibility). 
  
I know a lot of this stuff has already been discussed and perhaps cleared, but (and this is only if I were patient enough to not toss a rock through the glass), that's how I'd trouibleshoot it. 
		
	
		
		
		
		
			
		
		
		
		
	
		
		
	
	
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