I dont think a dual bulb fixture is going to be enough to have a brain coral do very well. It may do "alright" and not die but to have it grow and thrive will require in my opinion 2 more bulbs.
I've had pretty good luck with alot of coral and the smallest fixture I have is a 4 bulbs t5.
As far as dosing, a really good rule to follow is to not add anything you do not test for. Almost no tanks need iodine additions and calcium and magnesium are only dosed when you have a full tank of corals that are sucking down those elements before you can do a water change. A good water change is all you need to do to elevate those levels again as most salt mixes contain enough of every trace element that you wont have any issues with running too low. I am running 8 tanks right now and rarely if ever dose anything. I have a 125g with a good amount of coral including some very large ones and have no need to dose regularly. When I had SPS and hard corals I used to dose for alkalinity and that was it.
Adding things to your tank just makes you play catch up and sometimes does more harm than good.
Just my 2 cents!
