Cup coral?

[Nrm]

Does anyone have a clue what this critter is? My tanks been running since the end of January and I’ve added nothing new In awhile and it just appeared. I’ve seen some critter IDs that look similar and they said it looks like a cup coral. Should it be spared?
Also I just noticed an asterina starfish too, should I leave it be? Thought i would include that too.

 

[BryanM]

That could be a majano, if it is most of us believe them to be invasive and bad.

 

[EricR]

Is your rock live rock from the ocean? If so, where from?
Tentacles do look (to me) like what I've seen ID'ed as "hidden cup coral" that often comes in on live rock from the Gulf.

*not sure but that seems like a good guess, depending on where your rock came from

I'd leave the cup coral if it were me but get rid of asterina/aquilonastra stars just for fear of them having a population explosion.

 

[Nrm]

Is your rock live rock from the ocean? If so, where from?
Tentacles do look (to me) like what I've seen ID'ed as "hidden cup coral" that often comes in on live rock from the Gulf.

*not sure but that seems like a good guess, depending on where your rock came from

From what I’m told it is live rock from the ocean. I don’t remember where it was from. (If they told me)

 

[Reginald Reefer III]

Yes I believe that's correct. I have a similar hitchhiker from GLR.