iron is a trace element
That's right - trace. That means it's required in small quantities - not large quantities. Iron does not cause hair algae, it won't make your plants grow better (on its own) and you really need to stop focusing on it so much.You're also very unlikely to have only an iron deficiency, because nutrients are all generally linked.
Those of you who are wise will know that there are far more important things to be concerned about such as good water circulation, lighting on for no more than 8 hours per day, minimum 30% water change per week (and more if you are having algae issues) and adding quality fertilisers on a daily basis.
So does iron ever need to be dosed separately? You probably know the answer to this by now but for those of you who haven't worked it out then no. You just need to add more of your main fertilisers, that's all. Neutro T and Neutro+ cover this.