Seachem Flourish Potassium contains 50,000 mg/L of potassium suitable for the natural planted aquarium. Potassium is one of several elements that are vitally important to maintaining a vigorous level of growth in a planted aquarium. Potassium can become depleted in a rapidly growing system or when the source water has a low mineral content. In these cases potassium could become the limiting factor to growth. Use Flourish Potassium to prevent potassium depletion (signs of which include yellowing in older leaves) and maintain the highest level of growth.