Rallos
Member
This is what I use for an ATO on my pico office tank and it's amazing! Way better than a float switch that always seemed to get stuck for me. Optical sensor that goes inside the tank so it will work if you black out the back, and no moving parts to get stuck/fail.
http://www.bulkreefsupply.com/smart-ato-micro-automatic-top-off-system-autoaqua.html
http://www.bulkreefsupply.com/smart-ato-micro-automatic-top-off-system-autoaqua.html