Well, from my experience I still couldn't give you a definitive answer on that. The first cleaner wrasse we had was completely fine with clams at first but started bothering it months after the clam has been in. The one cleaner wrasse we have now also occasionally picked at the clam. Keep in mine that, they only really irritate the clams but not eat them. However, this also make the clams not open up completely during photo period.