steelwool

I use steelwool only to reduce Po4, the rust is mechanically removed. I wondered how much Po4 is bound per gram of steelwool. I use 0,8/1gr per 400l to remove 0,04ppm.. however, last time I needed 8gr within 1 week.. to reduce Po4 from 0,12 to 0,08. So I think 0,36 ppm leached from my...