The night mode is set to come on at the same time every day for a specific duration. I don't recall what that duration is. I think in night mode, it runs the pumps on constant at I think 50% power? Not really sure because I don't really use it. Feed mode is triggered manually by holding down the button. Runs the pumps really low for 10 min then automatically goes back to the previous setting.
Not sure about the mag12. Not really familar with it but you should calculate the flow into the tank after headloss (vertical distance traveled, bends, elbows, etc..) there is a calculator on this site somewhere I think. Whatever you are flowing into the tank, make sure your drain can handle, otherwise you can over flow. As for flow through the fuge, I think the target is 3-5x tank volume.