AQUA MEDIC pH Controller without Sensor The pH controller is a precise tool for controlling the pH value in aquariums. In conjunction with a CO2 system and an electric valve, a stable pH level can be maintained, and the CO2 supply to aquatic plants can be controlled. The unit is equipped with a large LED display and a digitally adjustable control range from pH 3.5 to 10.5. The adjustment direction can be set upwards or downwards. The pH controller has a BNC connection for pH electrodes. It is recommended to use an original Aqua Medic electrode with a plastic shaft.