Potassium. Used in large quantities by aquatic plants, Potassium is one of the three main nutrients (called macro nutrients) central to plant growth. It is absorbed by aquatic plants as potassium cation.

Potassium is an activator for many enzymes and is central to leaf growth. It is integral for the osmoregulation of cells and tissue and stabilises the pH of cells and plant tissue. Potassium is also vital for photosynthesis and a host of other biological functions. If levels of Potassium are low, many metabolic processes in aquatic plants are stopped, making deficiencies of this macronutrient a significant concern.

Potassium is absorbed in large amounts second only to nitrogen, often in excess to what is required, and stored inside the plant until needed.