[rustybucket145]

Nope, Calcium Alkalinity and Magnesium are the only additives MANY people dose. Nothing else is necessary and many believe dosing others such as 'Essential Elements', Iodine...etc could be bad for your tank.

You have no way of testing 'essential elements' or iodine so how do you know they are low in your tank? What would be a good level? Do the corals actually even need them? How much do they need?

All of these questions are pretty much un-answered in the hobby and there are so many tanks that do NOT add them that are very successful it's hard for me to justify spending hundreds of dollars on something that 'may' help.... when in actually it 'may' do more harm than good.

I'd suggest checking out Randy Holmes Farley's articles on reef chemistry.. I don't have the link on me but I'm sure somebody will chime in with it.