Also check out Level-Loc. I was at IMAC last year and Premium Aquatics brought this guy with them who sells this ATO unit that he invented. I use it on my tank now and the setup is the easiest piece of equipment you will ever install. Plug it in for the Solenoid. Then hang on your sump, then plug the RO/DI water line into the side. DONE! This item is also endorsed by Anthony Calfo. Super easy to adjust water level, and has dual shut off floats. And it is $89-$99. Awesome!