Joe's Juice will make em multiply. I used to use the stuff, but I swear, every time I inject a big one, I get five to ten little ones growing around that spot in a week or two. I got a Copperband and it did very little to nothing. The only thing that I have success with is my burgess butterfly fish, but it can only get the one he can reach. Ones in deep crevices, he does nothing but annoy em and the aiptaisia don't extend all the way.
I added some Berghia nudibranches, two weeks ago and was worried they were dead, but I saw them last night crawling around some infested rocks. The rock that I placed em on had a few aipatias in deep crevices, but I can't see them anymore. I think it's too early to say if the Berghia are eating them, but they seem very promising.