I have not introduced pulsing xenia to this tank, although I had xenia in my other tank that was trasferred over. It isn't pulsing, but is still very small. I intentionally did not move any xenia over. Doesn't look like aiptasia to me. The rock is previously live rock from Marshall Islands but has been dry for 5 years before I set it up in my system mixed with FL gulf rocks (other side of tank) in March.
Any thoughts? I only noticed it because I was about to place a coral there.