Well I do believe it would still be the same Playa0069u. The way I understand the refugium. If I took my first container out (Water coming in) and moved the plumping into the second container (refugium area). Removed the last container (return) and moved it into the refugium container (which is not a good idea) very bad for the pump. I would still have to provide proper movement from the refugium to the tank. The turn over requirements would still be the same - at least that is what I believe. Otherwise you will have all kinds of problems with algae in your tank (cyano along with others). If you have a one inch pvc without any elbow, tee etc the flow is 600 gph, you need a pump to move it back into your tank or yes it will over flow. your pump MUST match your input - that would be critical and if the pump every failed the refugium area must be large enough to handle the tanks lowest point.