Do you know what species of anemone? When they have a natural existing symbiotic relationship there is a better change they will pair. As mentioned, there is no way to tell for sure. You can not simply force this relationship to happen, might...might not...might be a while. It took about four months before my rose BTA began to host my pair of percs.
Some people are like slinkies...they serve no real purpose yet can still bring a smile to your face when you push them down the stairs!:p
Have a great day! Brian