Complete black outs do not work in planted tanks. For your algae the easiest solutions are 1) bleach solution dip (ask for more info, and this is only a fast solution, but not a long term solution) or 2) raise co2 levels. This can be achieved by flourish excel, or just upping your reg. The type of algae you posted is not often caused by excess iron, but rather phosphates. This is a difficult thing to control, and is much easier to try to limit, and keep plants growing fast with good lights, and good amounts of co2.