I somehow got them in mine as well. Saw them first about 6-8 months ago, and kept multiplying. I was concerned at first and tried to eradicate them, but they were in places I couldn’t reach, so I let them play out...
Now they are just “there,” but they don’t seem to bother anything.
Incidentally, I’m also battling digitate hydroids in the tank. (They DO bother some corals.) But as I’ve searched for a solution for them, I found people say a medication, Fenbendazole, which kills hydroids also wiped out their vermitid snails (along with all the other snails and some echinoderms). I bought some on amazon... the product is called “Fish bendazole.” I’m trying to battle my hydroids with peppermint shrimp before I use the stuff (hate the idea of medicating the whole tank) but if I do, I’ll let you know the result...