The flow of the Marine-Pac 3 is sufficient so that in many cases an additional circulation pump is not required.
If you do need more flow however the Vortech mp10 pump is recommended. The best place to install it is on the right hand side towards the top of the tank.
The external motor means no extra heat is added to the water which is useful when trying to control water temperatures during summer.
Additionally it will brush away any bubbles that get trapped under the top glass.
Other cheaper options like the jebao wp-10 will also work but may add heat to the tank.