I put 50+ peppermint shrimp in my tank and they never touched them, and if you think you only have three, you are delusional. Not only do they multiply, but when disturbed they jetison pieces that become new ones.
And they are not just ugly. They can take over a tank in a matter of months and kill your coral. They have a nasty sting. Plugging them up with 2-part epoxy has been reported to work. Joe's Juice never did a thing to mine. They would retract and come back out a week later, as is the case with EVERY aiptasia fix I have tried.
if I just had a couple or so, I would remove the rock and soak them for a couple of weeks in RO/DI. Then place them in a QT and watch for a month.
This is a tough lesson to learn, but I ended up with thousands of them in my tank, some 3 & 4 inches across or larger. I now have a CBB which keeps them entirely under control, and I grow them in my overflow. I have 100% floss filtration on overflow water so they cannot take root in my sumps etc. any more. Then occassionally I place a rock in the overflow so they will attach, then give that rock to the display CBB so it can have a treat.
First things first, run all overflow water through floss or socks immediately, or they will get into every part of your system.