I had a couple of aptasia AND some mojano pop up when I was first filling my tank with LR. I got on this site and looked for ways to kill these critters. The syringe method may work, but getting ahold of a syringe it a royal pain in the rear - since I don't shoot heroin - and I'm not diabetic. I went to all the pharmacies in town - and nobody would sell one to me.
Alas, I came up with a (dare I say it) BETTER way to rid my tank of these pests. Use some reef epoxy (your LFS may sell it) to form a small ball, and then squish the 'lil
[hr]
into the rock from which they are growing - entomb them! Just make sure that you cover them completely - or they'll pop back out. After I had eliminated my tank of these guys, I put another blob of reef epoxy above their grave site and attached small shell - looks like nothing ever happened.
Just my thoughts - have fun killing those guys WITHOUT A NEEDLE!