I have the optical level sensor and mount. I was going to use it for an ATO system. But instead I went with a Tunze ATO. So now I have this sensor available for a me to repurpose it. I would like to utilize the sensor as a low water sensor in my ATO tank.

So how do I set this sensor up to give me an alarm when my ATO tank water gets to low?

Presently I have the sensor mounted underwater at the point I would like to know to refill my ATO tank.

The alarm would have to go off when the sensor is no longer covered by water.