I think it is important to note that it is insoluble iron that causes the red color. My understanding is that iron bacteria convert a soluble form to an insoluble form. pH will also affect solubility, but I do not know the particulars.
RAH,
That may be the case with the iron bacteria but the iron in itself in ground water will create a red color once it oxidizes and it's exposed to oxygen. Interestingly my homemade iron filter for my RAS' goes from a red to a light green and then clear as it filters out the iron.
