There's a product on the market that claims it can kill all pest anemones You could also try injecting them with lemon juice that can work as well good luck
FYI peppermint shrimp will take care of the small ones and very rarely medium-large ones. VERY RARELY. By small I mean smaller than your pinky fingernail. For the rest use Aptasia-X. I've had a breakout and have experimented with everything from lemonjuice to hydrogen gas to ultra powerful lasers and everything in between.
3 is how they live and hunt. Also if you can get wild not tank raised. The wild ones will go straight for them due to instinct while some time the tank raised aren't sure and will eat other things first. This is what I've found while using both.