The PEM L101-05 float switch sensor, with water level differential and height adjustability, when linked to a PEM L101-51 control panel, manages water levels in a fountain pond through a solenoid fill-valve or functions as a safety shut-off; when paired with a PEM L101-71 Control Panel with two sensors, it allows unlimited water make-up or both water make-up and safety shut-off, with easy post-installation height adjustment.