Smart ATO Micro fills up tank at night.

I have IM 25 Lagoon and have my ATO positioned in the return section in the middle. The ATO works fine during the day with no issues but at night is a different story it fills my tank to the brim every night. My lights run all night in a lunar blue mode I have even left lights on all night thinking it would help the optical sensor see the water level. But if the light is not in the same room it pumps about every 2-5 mins which fills up the display section every night. It hasn't ever over filled the tank and it has only gone to the failsafe once. I have to unplug the ATO every night to make sure it doesn't fill my tank and throw off my salinity. Please, any help that you can offer would be great.