Yes...
The overflow box will draw water from the surface of the tank and through a siphon draw it over the tank wall and down some type of pipe to a sump/wet dry down below the tank.
Once processed, the water is returned via return pump and repeat.
Some key things to note:
Some siphon overflow box designs can be prone to break siphon, however mine uses a U-tube and has never broken siphon on me. People's mileage may vary, but that's my experience with them.
Another key is to pay attention to the flow rate of the box. You will only be able to return approximately the same amount to the tank so that you don't push more water in than the overflow can take out. they don't have to be identical, but they need to be in the ballpark.
Because you would have a method to pull water out of your tank, it would replace drilling your tank. That said, if the tank is empty, you may want to consider getting it drilled, as it will not have a siphon issue at all.
also since we are on the subject, another key to think about is on a power outage, there will be tank water that will drain back to the sump/wet dry. It has to be big enough to hold the extra water or you'll get water all over.
Hope that helps.
