Well, now that we are on the subject of getting rid of them, This is a couple things that have worked great for me, even on larg Aptaisia!!!
Their both easy to Kill! you can use one product by kent marine: Lliquid calcium, when it's time to dose some calcium just put 5ml. to 10ml. in a syringe and let em have it!!!! Your calcium goes up, your majano's/Aiptaisa DIE!!!
Or another product by Seachem: Reef Carbonate, same as above.. It is reccommend that you have the appropiate test kits for both Ca. and Alk. and Ph. I use the amount specified by the directions for my tank..
It may take a couple rounds with a good size aiptasia!