Looking around it looks like Camel Shrimp will eat them, chocolate chip stars, and tiger cowries (none of these are remotely reef safe). Boxfish/cowfish are also reported to eat them, and semireef safe (though it is extremely important not to stress them as they do release ostratoxin into the water when stressed). Wrasses in the Halichoeres genus will also eat them, but they will eat any shrimp you might have as well.
Hope this helps.
Can I ask why you want to get rid of them? They have to be eating something, do you keep SPS or gorgonians? are you concerned about them competing for food? If you manage to get rid of them with out reducing their food supply you are going to have to find some other way of taking what ever it is that they are eating out of your tank. I think the filter sock is probably the best way to deal with them, just starve them out.