I have a sunset montipora that has had issues growing as well as my other encrusting montis. It has taken me a while to figure out the problem but I have finally identified it as monti eating nudibranchs (finally have seen them).

What is the best way to treat and eliminate these nudi's? Most coral dips I have tried are of no use to this problem.

Eric Borneman had an article where he talked about a potassium permanganate dip being effective, I'm pretty sure you can find it in the swimming pool section of sears. It's got a high death rate though, either way you'll need to remove and qt all montiporas for at least a month since they can live in your rockwork. Best of luck, those are the worst pests I ever had to deal with, had them three times and every time I ended up just having to toss out every montipora in my system.

You can try manual removal. Try to syphon them out. Also look for eggs.

Just wanted to say here is what has worked so far for me. I took a couple of frags at first that were being eaten by the nudis and treated them. The treatment I used was a prolonged dip (30-45 minutes with a heater and air pump in bath) in Revive. One week after use my sunset montipora is looking better than it has in a month and I have seen no nudis. I will update again later to confirm no new hatchlings. I plan to dip all my remaining montipora frags this weekend to make sure I have gotten everything.

You didn't check for or manually remove eggs?

Keep me posted on how many nudis are in your tank come the end of november...

I did inspect the pieces for nudis and eggs. I have seen none since the treatment. Treated twice spaced out apart to be sure. The piece most effected is now bright and growing once again. All effected areas have healed. I will continue to keep an eye out for sure though. The treatment did however help.