Meds for internal round worm

[SeaKing]

Looks like the tang I bought a last week has internal round worm. He spent the first nigh in the display tank but didnt look like he was doing well the next morning. He has been in QT for a week now but has not been doing so good. This morning i noticed this long curly thing out of his bottom. I think it is internal worms. Can anyone suggest good meds? Should I remove what is sticking out?

Could he have infected my other fish overnight?   

Thanks.