I have no friggin clue what the hell is going on it only happens when I refill the ATO tank. Sensors are working perfect but I don't like the one sensor because it's an optic sensor. The JBJ sensors are both float sensors which is a much better sensor IMO.

Greg when you refill your reservoir is the highest point higher or lower than where the export drains?

If its lower your back siphoning your reservoir into the main tank, lift the tubing up a bit and it should fix your problem.

That being said I have used the Tunze ATO for 6 years now, has worked flawlessly for me the whole time and I have not been nice to it (dry pump left right and center).

And if you want to be part of the Zoaelite tiled, radion, sweet a$$ shallow cube club you need to go Tunzee :razz:.

Haha. Alway one step ahead. Ill grab one tomorrow