The JBJ Nano ATO is the perfect upgrade for your aquarium. Our most reliable auto-top-off system is reimagined with dual optical level sensors for ultimate precision. Enjoy the compact versatility of a digital sensor without compromising the security of overfilling your tank. Installation is quicker than ever, and everything you need to get started is included in the box. The included protective cover prevents tank inhabitants from covering the optical sensor. Additionally, the protective cover reduces sudden changes in light or water surface disruption from affecting the sensor. This ensures accurate water level measurements every time. The complete waterproof design allows the sensor to be mounted virtually anywhere. The magnetic mount can hold securely up to 15mm glass thickness.