welcome to the world of aptasia management . Im sure you will get tons of folks suggesting products, but they will kill the aptasia, but cause it to spread. The goal is to keep them out of the DT. I have 7 systems and every one has an aptasia predator or predators.
Its like algae. You don't eradicate it. You manage it.
Build a balanced mini ecosystem. You don't want algae, so you have Tangs. You don't want flatworms, so you have wrasses. You don't want aptasia, so you have peppermint shrimp, aptasia eating file fish, orif your tank is big enough, and you are experienced enough in the acquisition and care of, a Copperband Butterfly.