I bought a live rock from lfs
that had about a dozen on it. I didnt realize it until i got home. Some lfs
like them in their tanks to feed certain specimens. I asked the lfs
store what to do and they told me the best way to rid them from your tank is to bring the rock back to the store and put it in their peppermint shrimp tank. They were all gone after 20 minutes. If you don't have that option they gave me a lime extract powder that makes a paste. The paste is meant to be injected into the hole the aiptasia is recessed into and every time it tries to come out it hits it. Intern it virtually melts itself. I also learned Through research that when you agitate them in the tank they multiply, so I would recommend taking the rock/rocks in and also buy a peppermint shrimp. Just thought I'd let you know how my aptaisia problem ended.