overflow to work with surge device

[Saxe]

I am designing a 120 Gallon Reef tank. I want to use a 25 gallon refugium and a cross current skimmer. I read about using two surge devices set for different quantities to vary times. This sound great. However I read that you should be getting your surface water to your skimmer. How do you set up an overflow to work with the Surge devices and still get surface water. I estimate a 1 to 4 inch water level fluctuation using 3 and 5 or 5 and 7 gallon surges. Thanks in advance.

 

[Anonymous]

hi.
Are you considering add a sump to the system? If you do, the surface water will to the the sump, where it will feed the skimmer. The surges will dump the water into the tank, and empty into the sump.

 

[Saxe]

looks like I will have to. Does anyone know a handy formula to determine the capacity requirement of a pump(how much should be in the sump at all times). For instance if electricity goes out I will assume my skimmer and surges have all emptied (worst case) That quantity of water will have to fit in the sump plus the water that should always be in the sump. I need to have enough water that if the electricity is out and the surges are full and power comes on I need enough water in the sump to supply the pump until overflow starts again. The reason I am worried is I only have the space below the tank for a sump. So I have to plan carefully.