Please help identify

[sailfin tang]

What is the polyp in the third pic?
Is it the bad kind?

 

[mscarpena]

It's bad. Kill it. It's a bad anemone.

 

[fishissues]

pest pest pest i kept one of those for a couple of months with no spread tho til i found out it was a pest...

 

[babyb]

yep its aptasia

 

[sailfin tang]

Yeah that's what I was afraid of.
What does pest mean? Do they spread?
Kill it how?

 

[babyb]

pest means they sting corals, they spread really fast, and i have seen some that are pretty big, and they are just ugly ( i think)
you can get joes juice and follow the directions and it will kill it or get lemon juice or boiling water and squirt it in there mouth and it will kill it

 

[babyb]

beautiful clam btw

 

[sailfin tang]

Do you inject it with a syringe?
Do you do it while in the tank?
Is the mouth the middle top?