Safely lowers pH of tap or aquarium water when used as directed, When used in conjunction with Kent pH STABLE, it will provide a buffered, acidic pH in the system, The use of a good pH test kit is absolutely necessary while using this product, and the use of an alkalinity test kit is strongly recommended! Many electronic pH pens and probes drift over time and frequent calibration with a good test kit is strongly recommended! SKU: RPS13446