The HYDROS Water Level Sensor contains no moving parts that can fail. It’s extremely tiny: it’s a little over a half-inch thick with a circumference the size of a US penny. The optical eye is magnetically coupled with the magnet side measuring only ¼” thick. It can be mounted to most clear, tinted, or painted surfaces up to ½” thick. The sensor operates in the daytime or complete darkness so it’s safe for use hidden inside your aquarium stand or in the back chambers of an all-in-one aquarium. The sensor is easy to place, easy to move, and easy to clean. The sensor connects with any HYDROS Sense Port using an aviation-style plug for safe operation. No additional power source is needed to run the sensor.