refugium overflow question?

[doxponygirl]

I have a 10 gl tank which is going to be used for my refugium to a 55 gl. tank. The refugium will be setting up towards the middle of the main tank for veiwing. I have the pump and tubing to put the water back into the main tank from the refugium. Now for the big question: How do I know what size of tubing to use for the gravity pulling the water into the refugium? Can I use a small overflow for this, in the same manner as wet/ dry system?

[doxponygirl]

I found the answer to my question!!!!!!! I have decided to just let gravity do all the work for me by placing the refugium above the sump and lower than the tank. Thanks any how!!!!