I have had that kind of HA, just not quite that severe. 
I am very close to no HA now. 
What I did/ used, were: GFO, RO water for top-off and changes, water parameters watched and dosed closely to optimal ranges, about 10 MEXICAN Turbo snails/130 gal (don't get any other kind, they don't work for HA), and a seahare. 
 
Then practice patience. One day you will look at your tank and goes, wow, there is the end in sight! I now have sold all of my Mex snails, except for three. And the tank still looks great. 
HTH. Lenny. 
		
	
		
		
		
		
		
	
		
		
	
	
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