Get it out of your system and remove the coral and put it on a new plug. I don’t really worry about aiptasia, I’ve never seen them irritate or kill a healthy coral of any type. I have them in my system and blast them with aiptasia x maybe every month or two when they seem like they need a pruning. Some of the most beautiful reefs I’ve seen have aiptasia in them, it’s not the end of the world. You just gotta take steps once there in to mitigate there numbers when they seem to have a growth/spreading spurt. If you have it on just 1 new corals plug eliminate the plug. It’s possible you have others that just aren’t visible, check your overflow compartment. They are not like having nudis, flatworms, bugs etc... here is a pic of my reef that has lots of aiptasia, but they don’t harm a thing and unless your staring personally at my tank they aren’t to visible. I wouldn’t sweat it. I understand not having any is a plus as it’s one less thing to deal with put they are not coral eaters so I don’t worry about them one bit, I just control them to keep their
#s in check from taking over a rock or 2, as they like to spread if left unchecked.