H. Aurora question

[GoReefin]

Had this guy in my tank for several months now and was doing a water change and scraping some coraline algae off the glass when I startled the anemone and he buried himself in the sand in less than 2 seconds and has been hiding for over an hour now. Is this normal behavior for these guys or should I be concerned?

Before

After

 

[GoReefin]

Good news he is finally starting to open back up! From research it appears these guys can bury themselves completely in the sand if they feel threatened.