I do not recall ever seeing a green majano, and the picture's not the greatest (no offense), so with what I can gather, it could very well be a tuilp anemone.
I have a very similar anenome only it has red tips. Have no idea what it is. But it is cool looking. So until it starts doing harm, I will sit back and watch.
i got one of those in my tank plus some aptasia mot cool i got to pepprrmints last week they havent done anything to them i had thought that it was an anemone ? but i found some info at barnes and nobles . i still cant figure out how to kill it. i thought my pepermint shrimp would handle it? mines has some pink and green theres only one so far.
inject one of the following with a syringe directly into it's mouth
Boiling hot water
Kalk paste (very thick solution of kalkwasser and RODI water)
Joe's Juice (commercial product)
Aiptasia X (another commercial product)
all of the above should kill it... there's probably more that will do it in as well.
Syringe+Boiling water, 2 doses.....nothing but vapor. Nice clean spot on the rock now. To bad they can't be civil and play nice with everyone else.......