OK - here's what I'm thinking. its pretty ambitions, but, I think its possible to do this without powerhead, or at least with very minimal additional flow
The closed loop will utilize both
1in and
3/4in RFGs with 4 man outlets. Since you'll be using the Abyzz A400 as your Closed Loop pump, you will have plenty of flow to drive this many RFGs
here's the overview - starting from the end of the tank to the back wall
Outlet at the end of the tank will be a manifold with 4,
3/4in RFGs on stand pipe that you can be set at various heights.
The two in the middle and on the back wall will act as drivers to push flow down the length of the tank, with the 4 at the breaking up the forward flow. This will create a nice and strong, randomzied undertow that will draw its way back to the drain on the back wall.
The return lines from the sump will flank the overflow and have 1in RFGs - one on each side the the overflow.
Obviously, run this past your tank builder and make sure the bulkheads positions and sizes will work.
What do you think?