Yes very helpful thank you. I normally change rez every week, it something my friend told me to do when he help setup my first grow. I understand what you mean about going to the store to get more nuits $$$ adds up quick. I added calmag twice already at the beggining of water change, hopefully I didnt hurt my girls. I'm going try it this way & see how it works but I would like a copy of your method/regiment for my next grow.