Hi, the Aiptasia I got in my tank had the same exact look but it was living in the holes of my live rock and had a deep rose color hue to it. I bought Red Sea Aiptasia-X. It was very easy to use.
1) Turn off your filter, return pump(s), circulation fan.
2) Attach the syringe top (straight or angled).
3) Shake the bottle of liquid and plunge a small amount (anything not used has to be discarded once it has touched saltwater. It comes in a liquid form which was easily plunged by the syringe and easy to wash out of the syringe too).
4) Put the syringe in the center of the Aiptasia and lightly squeeze. It covers the Aiptasia and they die pretty instant!
5) Wait 15 minutes before turning on your filter again.
Because it so easy to do, I just inject as I notice them. It also killed the majano anemones I found which look really similar but have a tiny bubble tip.