Nano overflow box - up and running update

[bkelly]

I have a 5 gallon standard hagen non drilled nano. its been running for 6 years and this summer i have had heating swings , probably due to the higher humidity from all my other tanks. I have a frag tank running off my main display right beside the 5 gal and thought it be nice to connect the nano to this system. Because its not drilled can i use a small overflow system to do this? Im not sure how overflow boxes work. Id need some way to ensure no overflow. The drain off could be plumbed into my main sump no problem but would need a pump to add water from the frag tank.

anyone done something like this.