I don't think it is nessasary to test for iodine... but it is a very important element to be adding. Iodine helps soft corals grow, it is good for treating infections, and it helps corals create pigmentation (you get a good looking tank because of it ) The test kits are really combersome (at least the ones I have used). Plus often they don't give a reading. Iodine is very difficult to overdose on anyways (not that you should try because you can). I would add it per manufacturer instructions and you will be fine.
Luke
Yah, I would definitely reccomend iodine. I did'nt use the stuff at all for the first 3-4 months I had my tank going, but I started using it and saw dramatic color enhancement.
I would reccomend iodine as well.
I had a problem where my shrooms were just melting away. Some very helpful people from this board suggested adding iodine. I did and every sense I have had no problems with the shrooms.
Be careful NOT TO OVERDOSE. If you dont test for it than watch the brain. If it seems all puffed up all the time you're probably overdosing. The Seachem brand claims that you cant over dose with their product I can neither confirm or deny. Just be careful. Have a great day!