I have 15 Aptasia in my tank, They killed one small fish in 5 months, i used huge and i mean huge amounts of kalkwasser mix for three weeks, it caused the ph to go nuts up to about 9 or more, the Aptasia retracted into the rock and started to die, but it was so hard on everything else in the tank that i had to stop, i decided to just leave them be until i get a few Copper Banded butterfly fish, that a want really badly anyways, Aptasia is thier favorite food. If i was going to try anyother way and im not sure if it will work is to take the rock it is living in out and put it in a container with saltwater and grind out the aptasia then rinse the the rock with fresh saltwater several times and Quarantine the rock in a separate tank for a few weeks, untill you know it wont come back.