what water said seems to make a lot of sense.
So if you are setting your ppm to 400, when it hits 200 in the reservoir, add more nutes to bring it back to 400 (or 500, or whatever)
Illusion Reviewed by Illusion on . PPM Question So I just got a TDS meter on Friday and I have a question, but here is my info first: My tap water is around 300 ppm. I changed my res for the first time on 9/28 and added 55 ml of nutes. On Friday (10/5), my ppm was around 500 or so, so I added 30 ml more which brought it up to around 700 ppm. Yesterday (Sunday) it was down to a little under 500 ppm, so I added around 50 ml more nutes which brought the PPM to around 875. My reading tells me that 1000 PPM is about average, and 1500 and Rating: 5