Blue tang illness? pics!

[Feralfable]

Watching my tank I saw one of my little blue tangs (0.5 inches) with a small scratch on his cheek after a water change. Knowing I had did a water change I suspected he scratched himself on a rock. Looking at him closely I saw on his other side was a big inflated thing http://oi53.tinypic.com/4snztt.jpg . It was definitely not there this morning because I had checked on both go them and I'm pretty sure it wasn't there this afternoon only after i did the water change can I say for sure is when he got it. I checked all my books and the internet but I don't know what it it.
The water levels where good before I had just changed the water to keep my routine, and the other fish aren't aggressive (or so I though) all I have in the tank is two clowns, a bicolor benny, a two spot goby, a cleaner wrasse and a few krono's and the two blue tangs or course in 120 gallon tank.
Could it be a mantis shrimp or a disease?
I'm setting up a hospital tank and it should be ready for tomorrow? And should I move his buddy with him?

 

[gbhayek]

feralfable, im not sure about the inflammation on his side, it could have been trauma from another fish, depending on how aggressive your clowns are. I had a clown that was so aggressive towards a blue hippo tang that he had to be removed. As far as quarantining him, there is one thing in the picture that makes me nervous, and it could just be your picture, but i see a moderately advanced degree of fin loss on the fish. He could have been nipped at, bit it seems to be too jagged and too advanced for that. So personally i would quarantine him and start him on a broad spectrum treatment to be safe. I would move his buddy as well only because it could reduce stress to have something familiar and it is very possible that they both have an infection. Keep us updated.

 

[Feralfable]

I don't think it was the clowns because there pretty friendly and shy, and still pretty little, I'll put them into the quarantine tank as soon as possible it's just I have to replace some equipment first, but thats for the heads up I didn't pay much attention to that and more to the warty growth. I will start them on the medication as soon as possible thanks so much for the input. Thanks again and I'll update as soon as things look brighter.