Kamoer ATO One 2 Small and compact Suitable for Nano/medium aquariums Blue optical level sensor for keeping water level stable Red optical level sensor for preventing overflow Very easy to install and adjust with the magnetic bracket Audible and LED alarm Submersible pump for meeting the needs of using freshwater reservoir Submersible pump supports freshwater shortage detection Flow Rate 230lph ATO One is a smart water replenishing device that requires only the sensor and the refill pump to be installed. It can be used after power-on without setting any parameters. The optical level sensor is used to monitor the water level to determine whether water needs to be replenished. The float level sensor is used to prevent overflow.