GMSgrowsanswered grow question 4 years ago Chevy is correct. 400 ppm to start and if you see good growth, in hydroponics, then you increase 100 ppm every week until you reach 8 to 900 ppm. Keep your water cooled and make sure your ph remains stable, adjusting as necessary every day. As Chevy says a good ppm reader is essential for hydroponics and just about any other way of growing. Cheers