In my tank I have an inovative approach to Iron.
I have several small iron magnets (origionally improvised plant anchors) that are slowly rusting away. It seemed to be sufficient for my plants when they were small, but now they aren't cutting it.
This method has its merits if your plants aren't iron hungry, the main one being that because rusting occurs at a slow and regular rate it should provide a constant, albeit small, source of iron for a year or more. Additionally it doesn't pose the risk of ODing your fish with iron.
Playin with Plants n Shrimp