Phosphorous is one of the main three macro nutrients nitrogen phosphorous potassium npk required by plants and can often become the limiting factor to growth in a flourishing systemr flourish phosphorus is a safe solution 4500 mgl phosphate of potassium phosphate that takes the guess work out of 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