Plants (including algae) require three macro nutrients to grow: Nitrogen, potassium, and phosphorus. Of these three, phosphorus is the often the "growth-limiting" nutrient. i.e. the local environment may have an abundance of nitrogen and potassium, but algae won't develop unless phosphorus is available too. | Plants (including algae) require three macro nutrients to grow: Nitrogen, potassium, and phosphorus. Of these three, phosphorus is the often the "growth-limiting" nutrient. i.e. the local environment may have an abundance of nitrogen and potassium, but algae won't develop unless phosphorus is available too. |