Unknown coral

[Mike-portocarrero]

Hello guys I have notice this little things growing all over my rock can someone Identify them and tell me what they are? Are they corals? They are alive cuz they feed they grab anything that passes by and they close up, almost like an anemone any ideas are appreciated thanks in advance

 

[Keithhjs]

Looks like Aptasia. Unwanted guest. Get rid of them as they spread fast. They sting corals.

 

[Mike-portocarrero]

Thanks for the reply they are all in one particular piece that I added it couple weeks ago if I take that piece of rock and run it under hot water for a few hours would that kill them? Thanks