My New 72"x20"x20" Tank Build

[mark]

Going from the photo, think about this.

Have the top of the sump and ref and about the same height. Inter connect with a large bulkhead as low as you can on the ref (no valve). Assuming the pump is on the far right of the sump with no baffles to the right, the water level in the ref will be the same as the pump compartment. Use a auto topoff to maintain.

Have no baffles in the ref other than a strainer on the bulkhead and maybe some eggcrating in front of the strainer. Negative is if the strainer gets blocked ref overflows so place a second interconnect at the top.

With the interconnect below no bubbles like Untamed said.

Not sure of your planned height in your in the pump compartment but adjust the ref height to max the volume in the ref tub.