I have to second the boiling water approach. The ones I "Juiced" are growing back, and they each ate a good amount of the stuff...
If you have a smaller syringe than a turkey baster, you'll put less scalding water into your system, and with less risk to surrounding corals. None of the boil-injected aiptasia have come back on me. But yeah, 2 or 3 squirts and they're done.
I like the turkey-baster removal part, though.
