+1 to Beengirl. Or a pepermint shrimp. I only had it 1 time and my shrimp took care of it. Shrimp since died and Aptasia never came back, so he had already gotten ALL of it. Some people say the Pepermint shrimp is hit or miss, but for people who try, seems pretty reliable.
One of my LFS had not been able to get the shrimp for quite a while and they were having Aptasia issues in many of their tanks. When they finally got the shrimp in they put 1 in each tank that did'nt have a preditor in it. Every tank was cleared of Aptasia.