kill it or let them grow?

[Graham_f]

hey, need your expertise.

first i found two of these little anemone things. one big(about .75") and one small (.25") but have grown from nothing. are they a problem? They are translucent with white tips and have a white center attached to the rock.
look kinda cool, dont seem to grab food or react much to touch.

kinda hard to see. dead center between the candy cane.



and then this little slug thing. It been hiding/riding on or around one of my Astraea snails. it had a hard backplate and is super fast... at least as fast as my hermits across the botton of the tank. caught him, now he'c chilling in a cup



thanks,
Graham