A water pump is a good idea as this will aerate the water. Though, I am a little suspicious as to whether or not the Iron will oxidize with the water to form Iron hydrates, you might want to research that a little. I can ask at the chemistry department if I have time, though I am really busy right now with other endeavours.
Try googling Iron AND Iron Hydrates on the internet to see if that brings anything up.
If you do find that this is a potential problem, you may look into sealing the pot with epoxy or some other sealant (sp?).