I agree with TippyToeX, something is amiss to cause the anemone to move. In the wild, if an anemone is forced to move (lack of food, microhabitat, proper flow, or light) it generally means certain death (though it is certainly not the same scenario in the aquarium, it just serves to show that anemones only move if they absolutely must). It will sting corals that are in its path, so that poses one problem. How long have you had it? Give some concrete numbers for your parameters. Try feeding the animal also, as this is one of the more common reasons, besides flow, for its movement.