peppermint shrimp SOMETIMES work, but when they do, they work well, they may alsoe eat polyps and or feather dusters instead (trust me)
another alternative si berghia, a type of nudibranch, that only eats aptaisia and nothing else at all, only advantage is once the aptaisia are gone, they need another home, or will starve to death
then there is also kalkwasser or pickling lime, mix a paste and inject it right into their mouths, works well, i had the besst luck with this method
HTH and good luck