That's a lot of stuff for a 40!  I think you will have problems with all those pistol shrimp in your tank. I believe they are territorial so you may have problems there.  Same thing with gobies.  Unless you know how to sex them, you might just end up with a whole lot of dead fish.  8 fish in a 40 is really pushing your luck IMO.   
 
So, you have 2x250GPH powerheads and 2x300GPH return pumps?  Did I read that right?  Just need some clarification. 
		
	
		
		
		
		
			
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