Yep, aptasia, best things I have heard were some butterflies and peppermint shrimp, at least for natural controls. Outside of that there are injection methods, manjaro wands (burns/electrolysis), and lasers that can help get rid of them. Important thing with wand/laser is to make sure you scoop out remains.
Jordan
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Edit: one more note regarding the butterflies, they will eat some corals as well. If you only have a couple, a single peppermint should do the trick. Once outbreak starts, you might need more depending on size of tank