My 3 peppermint shrimp took care of mine. It was only 3-4 that i could see that I couldn't get to myself. They seem to eat things like that at night and are real effective if you don't feed them for 2-3 days. Unfortunately they tend to eat anything when they run out of food. Hungry peppermint = evil peppermint
For the one I could get to I used pickling lime, water, and a syringe. Mix it like sloppy tooth paste and load up the syringe. Turn off all water flow, then try to inject them until it comes out, if they retract in the hole, just fill the whole. Use some air line tubing to suck out any extra of the mix, just leave a pea sized glob on them. It hold together real well when you turn the water flow back on.
I tried a majano wand. Uses a electrical current to produce hydrogen that disintegrates them. Its pricey, time consuming, can only get what you can reach with it, and fun!. Have to turn all water flow off, then touch them with the probe. They just melt apart and pieces float to the top. You then need to remove the pieces from the surface. Downside on this is you can only use it so long (in the minutes category) before the hydrogen gets to high in the tank. My 45 I get 4-5 minutes run time, which can stretch out to 10 minutes or so. There is a button you hold to turn it on and off, so it doesn't
run the whole time. Plus if you don't get all of the foot off the rock, it will grow back.
Last thing I dabbled in was boiling water in a syringe with a piece of air tube on it. Just boil water, put in syringe, spray aptasia closely and slowly. Do this 2-4 times. Then with syringe empty, put the airline on the syringe over the aptasia and suck it up. If done right it will release from the rock and go into the syringe.
To me, the best one I had luck with was the pickling lime (kawk paste) and a syringe. Just cover them and forget it.
Probably another 20 ways to treat beside these, but I don't have personal experience with those but others have and have had success also.