Glass anemone? Cup coral?

[B Lo]

So I found what appears to be a white anemone of some sort. I know it's an anemone as it has a foot and has moved around the tank from time to time. I don't know what type of anemone it is but I'm curious whether it's a pest species and whether it should be sentenced to die. I also spotted some little critters that appeared in patches where barnacles used to be on some live rock. They are so small, I can't tell whether they're some type of anemone or cup coral. Any idea? The big guy in the sand (first two photos) is the anemone. The clusters (photos 3, 4 & 5) are all on live rock. Any thoughts would be great! Thanks!

 

[Sierra_Bravo]

The last three pics look to be hidden cup corals. They will have a stony base when they retract their polyps. I have a few on them from live rock that came out of the Gulf of Mexico. They seem to prefer shady spots.

I've been told they can and will sting other corals, but they are so small and limited in my system I'm leaving them.

Here's a group I have fluorescing under a blue flashlight. Not all of mine fluoresce like this one; some are just brown:

Another pic when I first found them before they multiplied:

 

[B Lo]

Thanks, Sierra_Bravo! My LR came from the Gulf as well so your theory certainly seems likely. Now I'm hoping someone with anemone expertise can chime in on the big white guy.

The last three pics look to be hidden cup corals. They will have a stony base when they retract their polyps. I have a few on them from live rock that came out of the Gulf of Mexico. They seem to prefer shady spots.

I've been told they can and will sting other corals, but they are so small and limited in my system I'm leaving them.

 

[Maritimer]

That white anemone doesn't look like any Aiptasia I've seen before - but I can't tell you what it _is_, either.

~Bruce

 

[Ewelina]

The anemones are not aptaisia but I do not know the type.

 

[KJ]

Cup coral.