I battled aptaisa's for a while, I added a dozen, YES, 12 peppermint shrimps to my tank, hehe, they did a great job for me
Its hit or miss really...
I've herd the joe's juice works well, I have some and never used it as the peppermints did the trick for me, you can also mix up some kalwasser with water make it like a thick paste and smear it over the aptasia, it'll nuke it for ya. also some say to inject with boiling hot water...
I'd try the peppermints first, they are cheap enough and worst case if they dont work, you got some help in your clean-up crew
Do some reading if your gonna get the banded butterfly fish, make sure your tank will meet its needs...
I'm a good preacher of "reasearch before you buy" hehe