We can't post links but here is what another site had to say on the subject:
Anemonia majano
These are the prettier of the two common pest anemones. I have seen specimens in green, red, and even a striking yellow. They are somewhat less of a nuisance than Aiptasia, partially because they are somewhat attractive, but primarily because they are not nearly as prolific. They can be easily distinguished from Aiptasia because they have bulbous tips on the ends of their tentacles. Unfortunately, like Aiptasia, they have a potent sting and can become a danger to the other sessile invertebrates in the aquarium. Anemonia are Indo-Pacific in origin.
It said to use Joe's Juice or Kalkwasser/Calcium Hydroxide to get rid of it. Kalkwasser is cheaper and Joe's Juice is basically Calcium Hydroxide and some Boric acid anyway.