The tunze is a very reliable system and works well. It is used by reefers extensively. I am not sure how you would mount it on your tank though. Even if it is mounted at the very top of the aquarium you will need to lower the water level to be an inch or two lower than usual for it to work.
You can also look at autotopoff.com ATO's, they are reliable and I have had one working on my reef for over two years without issues. (You will need the ATO + a pump -> Tom's aqualifter.)