I know this sounds funny, and a little mean, but I fished my two 3-stripe damsels out of my 200 gal reef. They’d beat up any new fish I tried to add and I wasn’t about to break down my tank to get them out, so I went to a tackle shop and bought the smallest fishing hooks I could find. They were these tiny gold colored hooks (I don’t have the package anymore and I can’t remember the size). I used very light fishing line and baited the hook with a little nub of shrimp and just dropped it in front of them. It literally took only 5 minutes to get them both out. I only let the bait go a few inches into the water so it was easy to control where it went and keep it away from the other fish. The only problem you might have is if your damsels aren’t aggressive feeders. That wasn’t an issue with mine. It didn’t significantly hurt them either, other than being hooked in the mouth and scarring them. So you might try this if all else fails and you’re faced with pulling rock out.