A phosphorous supplement for planted aquariums. 250ml treats 500-5000 US gallons. Phosphorous is one of the main three macro nutrients (nitrogen, phosphorous and potassium) required by plants and can often be a limiting factor to growth in a flourishing system. Flourish phosphorous is a safe solution (4500 mg/l phosphate) of potassium phosphate that takes the guess work out of phosphate dosing. Unlike other products that mix nitrate and phosphate in a fixed ratio, flourish phosphate (being nitrate free) allows you to dose phosphorous according to the needs of your plants without the risk of overdosing nitrates. When used as directed Flourish phosphorous with enhance and accelerate the growth of aquatic plants without enhancing algae growth. For maximum benefits use with Flourish Nitrogen and Potassium.