Crap, that looks like a ritteri, as stated. Can you get a picture of your actual anemone up? If you have a pic, just PM me your email addy and I'll post it for you. I wouldn't even worry about it's potential future size right now, IF that's what you have, it's not going to live and could do it's share of damage in the meantime. But you may have posted a different specimen than what is in your tank. I can't (necessarily) identify it, but it looks like someone here probably could.
Good luck, and I'll be glad to host the picture...
Good luck, and I'll be glad to host the picture...