Its surface coated with living alumina as activator, mightily absorb phosphate and its compound to prevent algae from growing and expanding, 9times capacity of absorption than activated carbons. Meanwhile filter debris and particles effectively. Make use of Polypropylene Fiber, its porous structure bring the good filtration for debris and particles and very minimum resistance for water cycle, specially optimal for the last filtration. Other items like this could you pls take a look at our website: