Your overflow is only going to drain water from what's put in the main tank from the pump coming from your fuge and as long as your pump isn't pumping more than your overflow can handle then your fuge should maintain the same level and only lower with evaporation.
Since you have a 110 gal
tank you will have around 1-2 gal
a day evaporation and your fuge will need constant topping off to maintain the level. An auto-top off would be helpful for maintaining the level so you don't have to do it everyday.