Can someone explain how closed loop works?
 

I'm having a new tank built very soon & don't really understand how a closed system works, I know it gets rid of the powerheads in the tank, but where the hell do put the pump (mag7)?, in the tank?, outside the tank, do I get rid of my sump?

Confused, if I can get a good grasp on how it all works,I would think about doing this on the new tank, how many extra holes do I need drilled?, as of now, I was just going with the overflow & hole drilled in the back for the return from the sump?

Anyone?

Can someone explain how closed loop works?
 

Basically you take an inline (i.e. external) pump and have your intake(s) and output(s) in the main display. It is a circuit that is independent of the sump. Beyond that pretty much anything goes. I suppose you could put your pump in the tank if it's a submersible but realistically at that point it's more of an elaborate powerhead.