You can check the amount of nutrients using a PPM(parts per million) meter but it's not necessary. You should change your reservoir every week or two. I recommend every week. When you do this you should add the directed amount of nutrients and adjust the pH. The water level will go down each day, and when you top it off you should add a little bit of nutrients. Read the info on the link and you will find everything you need to know.
Nutrients Post #10395
hello,
I'm new to hydro systems and was wondering:
how do you check your nutrients mixture in your reservoir and how often do you need to add more nutrients/flush in a DWC bubbler system?