ID please

[Floop70]

Can anyone tell me what this lil guy is? He's about 1 CM across. Came on my liverock and seems to grow pretty quick. When it closes up it just looks like a small black mound on the rock. I've had one fall off the rock and it has now attached itself to the glass on the back of the tank. I have also seen a couple of them move to different locations and a couple others have split into 2.

Any help is greatly appreciated.

Thanks,
Bruce

 

[KUDA]

That is an aiptasia anemone. It is a pest and will spread rapidly and sting corals.

 

[WhiskeyReefer]

Hydrod/aiptasia......Pest!!!! Kill it!!!

 

[Tayler]

you can kill them by using a syringe and injecting them with joes juice or lemon juice.