Is this Aiptasia?

[SFREEF3R]

They look similar in scale/shape to other aiptasia I've seen, but the tentacles and coloration looked a bit different. Wasn't 100% sure on the ID. I'd estimate them to be 1/2" to 3/4" across.

 

[jgirardnrg]

Yup... sure looks like it

 

[AquaticExotics]

Looks like it, I would glue it in if you can. It spreads like wildfire if you attempt to pluck it. Peppermint shrimp in a lower flow area can eat it, in a higher flow zone a file fish would work better.