Montipora eating nudibranch

[rynoe]

So the other day I noticed my very large green monti suffering tissue loss. I kept an eye on it and started double checking all parameters in the tank. I could not find any reason for the tissue loss. After five days the coral was dead. I then noticed my red monti starting to do the same. I then stumbled upon montipora eating nudibranch on google and sure enough the underside of my monti was completely covered in them. So far the only treatments I have found are to be performed out of tank and that is not an option for me. Has anybody dealt with these pests in the past?