Hi Kim,
There are several ways to rid your tank of Aptasia. Natural remedies would include Peppermint Shrimp, Aptasia eating nudibrancs, Copper Banded Butterfly fish and aptasia eating file fish. You can also get a product like Joes Juice or Aptasia X at the LFS or make your own paste with kalkwasser and apply it with a syringe to the Aptasia.
I really like using peppermint shrimp, if you keep them hungry they will eat up the aptasia in not time and then they will keep it from coming back. The nice thing about peppermint shrimp over the nudibrancs is that they will become part of your Clean up Crew where the nudis will die if there is no aptasia for them to eat.
Get rid of them as soon as you can before they take over the whole tank.
Edited by bfessler - February 13 2011 at 3:42pm