Plant Pack Enhancer: NPK combines Flourish Nitrogen, Flourish Phosphorus, and Flourish Potassium. Flourish Nitrogen is a concentrated (15,000 mg/L) blend of nitrogen sources. It provides nitrogen in both the nitrate form and the plant-preferred ammonium form. However, no free ammonia is released because the ammonium in Flourish Nitrogen is complexed and unavailable until utilized by the plants. Flourish Nitrogen also provides nitrate for those plants that can readily utilize nitrate as well. Flourish Phosphorus is a safe solution of potassium phosphate that takes the guess work out phosphate dosing. Unlike competing products that mix nitrate and phosphate in a fixed ratio, Flourish Phosphorus (being nitrate free) allows you to dose phosphorus according to the needs of your plants without the risk of overdosing nitrates. Likewise, because Flourish Nitrogen is phosphate free you can use both products together to target exactly the ideal amounts of each for your system. Flourish Potassium contains 40,000 mg/L of potassium suitable for the natural freshwater aquarium. Potassium is an important element that is needed by all plants. In a thriving planted aquarium it can become the limiting factor to growth if it is depleted.