it will only take them down to 20ppm if u have water with zero nitrates( RO water)epond83;4348617; said:check your nitrates. If they are at 40ppm a 50% will brink them down to 20ppm figure out how long they take to come back up.
Dcide how often and how much to keep it at a good level.
40 ppm is an acceptable level, btw