I've used the glue method, breaking them off at the base, (you have to get the whole thing or they'll rebuild their shell) and injecting them with boiling water. You'll need a very fine neeele to be able to stick it in their tiny hole. In your case, being that it's in the SPS colony, your best bet would be to put a dab of glue over the hole. Trying to break them off or injecting with boiling water may cause tissue damage to the SPS. Good luck!