Youre looking at maybe a mag 7 I think with that overflow. Youre overflow will only handle as much water as what the pump sends up to the tank. If the pump is slower than the overflow then it will work still. But you are aiming for as much flow as you can get so yeah, measure out how far the pump has to push the water and take into account any bends or tees in the return line.
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.