I've actually seen these guys here and there in our lab. Definitely an anemone. The last and second-last photos are actually fairly good representations.
They don't appear to be any of the "pest" species ofAiptasia. They reproduce in the tank, but not rapidly, and they have a DEFINITE...
I'll be setting up my first saltwater tank soon(as soon as the %^*$^@!!! live rock is cured) after a couple of decades in the freshwater end of things.
I'm particularly interested in E. crucifer. The tanks we have in the lab where I work have given me ample opportunity to observe these guys...