The iron content in the formula is more than sufficient. If you are thinking about iron from the point of trying to get plants more red - invest in a better light instead. Iron only helps to maintain pigmentation, dosing more beyond a certain level does nothing. Our 2Hr Tanks do not receive additional iron other than what is in APT complete. It would have been easy to make a fertilizer with much higher iron levels, but we have found that it creates more problems with no visible benefit.