What are these??

[Brancho]

I've seen a few of these on my rock? What is it and anything to be concerned about or removed??

 

[Rmckoy]

Aptasia ( glass anemone )

pest anemone and should be removed

 

[vetteguy53081]

Removal is simple:
Using syringe, inject either lemon juice or better yet. . kalkwasser powder mixed with tank water into a paste the consistency of toothpaste and inject into the very center core and it will melt away

 

[Brancho]

Thanks I'll remove