Cool. I've never read or heard anywhere that clams could damage corals. Also, I can't really imagine how they could hurt your acro, unless they were some kind of mussel that just outgrew and covered your acro. Unless you see some kind of damage associated with them, I wouldn't try to remove them. I always get a kick out of the hitch-hikers that sometimes come with wild acro colonies, which is one reason why I still occasionally buy them, even though most of my SPS come from frags that are, on most occassions, multiple generations of captive raised SPS.
Best regards,
Ken
Happy Holidays!
