People try all kinds of crazy stuff on Majano when all you really need to do is scrape the Anemone off the rock.
Unfortunatly, your Anemone are Aiptasia. You cannot scrape Aiptasia off a rock because 5 or 6 will grow back in its place from leftover cells.
So, try all the crazy Aiptasia remedies, something will work.
I mix fish food, like Mysis Shrimp, with Calcium hydroxide and water to form a paste. I feed the paste to the Aiptasia and the high PH of the Hydroxide kills it.