Had a stuburnly high po4 levels. My no3 was spot on at 10ppm. I ordered a life time supply of sea clear to help get things in check. I used 1ml out of 32 oz for one treatment. Needless to say I have extra. Anyone that wants some can come get an oz. That should last someone a while even with 1000's of gallons. I dilute 1000xs litteraly. 1ml to 1000ml of ro water