@nanonøkk i understand your worry I feel the same way about mine. Darn anemone has me on edge.
Things to remember
If it is opening up during the day. If it is fairly stuck to its rock. If it’s moth is closed expect when pooping or eating. Than don’t stress. Enjoy it.
If it starts to always be moving. Or if it’s deflated for loooooong periods of time ( like most of the day durning day time hours) if it has a gapping mouth. If you see filiments (I’ll find the thread I made with my nem when it was actually sick). Than we can help you through treatment.
How long have you had him you had him?