spsick (above) is correct. The water level will go down in the sump , not in the DT. So your sensor needs to be at the full level in the sump.Thanks for responding. It uses an optical sensor that is a little over a half inch long. I think i discovered I had it incorrectly placed. It was in the display tank but I had it too low so when the water level actually did drop it didn't respond correctly. I love that there was the smallest sheet of instructions that only show the main setup and not the indicators or where ideally to place them. I hope and believe I might have figured it out?
Hope that helps?