I ended up having some a couple years ago. I was unaware I had them until I started dosing vitamin C and amino acids and they exploded in growth. I reasearched them and the only thing I know that will kill them is interceptor for dogs. DO THIS AT YOUR OWN RISK read up on it and make that call on your own
I removed any crabs I had and crushed a whole pill up and mixed it in a solo cup with tank water to dissolve it and dumped it in. After that I took the collection cup off my skimmer and let it over flow for a couple days. After 3 days I did a 30% water change and put the cup back on. For a whole week I watched and nothing happened, they were all still there. A few days later I looked and most of them were gone. I did a follow up treatment 3 weeks after that and have never seen one again.
To this day I don't know if the interceptor killed them or just everything they were eating so they just died of starvation. I know all my pods died and an emerald crab that I couldn't get out died. It did not effect my micro brittle stars or bristle worms. I also was very careful to just feed my fish the bare minimum to cut down on the xtra food floating around.
One last time, DO THIS AT YOUR OWN RISK!