GMSgrowsanswered grow question 3 years ago You need to feed by ppm, ec so as to not over or under feed. A ph ec reader is recommended. Autos start at 200 ppm 0.2 ec for their first week of life in hydroponics. Second week if you see good growth then increase to 300 ppm 0.6 ec, 3rd week 400 ppm 0.8 ec, 4th week 500ppm 1.0ec, 5th week 600 ppm 1.2 ec. Stop there.