i heard you can inject it with lime juice from a seringe. i don't know if that will hurt the pollips next to it though.
i got rid of my aptasia out break witha couple of peppermint shrimp. i had about 20-30 in my tank though, and so will you if you do not get rid of it quickly. i read that a moderatlky sized aptasia can produce up to 60 offspring a day
p.s. don't smush it becouse the bits that are lift in the tank can become new aptasia.
why are the bad things so easy to keep and the good things so hard
good luck