You know, this may sound silly, but the best way to rid a tank from aptasia is to keep the nutriant level in the water down, and to make sure that the water chemistry is right on. I had two (that I knew of) glass anemones pop up in my nano when I moved it to Arizona. However, when the cycle was over, and the water chemistry was balanced they went away. If they are not reproducing in your tank, and they are not stinging anything, patients may become a virtue. Just a thought.
M