Skimmer à Return ß Refugium
In this situation, the two outer compartments receive their water from two sources (or one supply line that has been split), and pour into the central compartment.
Benefit - Refugium wall can be taller, and the amount of water flowing through it can be controlled with a ball valve.
One objection often voiced is that “you don’t want to skim out the nutrients in the water going to the refugium.” This isn’t possible to do, unless every drop of water had to go through the skimmer to get into the refugium. Most of the water runs right past the skimmer! Even with a very weak return pump, the water pumped into the skimmer is only a portion of the body of water traveling into the next compartment.