Here is your answer:
For Aptasia- You cant beat a Kleini Butterfly BUT must be the bluehead- NOT the yellow version. The yellow will go after coral too but bluehead as pictured will eat aptasia like candy, then eat all dry and frozen food offered, colorful, friendly and stays small. I will note that a couple of persons who got the blue had their kleini nip zoa. if so- easy sell, or place in sump as aptasia have likely made it down there already but EVERYONE of them stated it got every single aptasia