I agree with jbvdhp, if you want a clown tang, why not try it. You can always borrow a fish trap and remove it. Sometimes I think we overthink some of this stuff. I am guessing most of the people who gave you advice have never kept them before. Get a small one and see what happens. You aren't trying to put a massive trigger in a nano. A small clown tang - why not give it a shot?
And Moeshi, chill out dude.