Closed loop set up, does it need an overflow?

[nbzak]

I just purchased my tank and the guy that will be somewhat helping be set it up said it will be a closed loop tank. I told him I wanted any overflow onit. Now, I'm having second thought after reading more. Do I need overflow? If not, is this a big mistake? hopefully someone will have a few suggestions.
Thxs nbzak

 

[myreef05]

No overflow needed. The water comes out the bottom or the back of the tank, comes to a pump and then gets shot back into the tank. The pump usually sits on the floor (out of the water). You will need to have a buffer of somekind under the pump so it does not vibrate/rattle.
Overflow is used to take the water out of the display tank and takes it to a tank under the stand, filters the water, and then a submerged pump takes the filtered water back up to the tank.

 

[dmitry]

Right, there's no overflow for a closed loop. Water comes out of the tank through one hole, goes into an external pump, which pushes it back into the tank through another hole (or two, it's up to you). When you set up the external pump make sure you put valves on both ends of it so you can shut off water-flow and and remove the pump without draining your tank.