For continuous, precise control of ozone or CO2 injections in your aquarium. Each unit controls upper and lower ranges, cycling your equipment on or off accordingly to adjust pH or ORP readings. Each has a large LCD display and includes a probe for aquarium use. Replace electrodes approximately every 18 months. Both units have an amp rating of 5, and accept 3-prong plugs. pH Controller includes calibration fluids. 9-volt battery required (sold separately). Electrodes , adapter kit , and calibration packets also available. Please click on "More Information" for further details.