FWIW, the sixline will not solve all your problems with this pests.You will have to manually remove them and be very dilligent with removing any empty snail shells as they will hide there as well. You have to understand that this lymphatic fluid suckers feed at night when your six-line is asleep and it is up to you to be dilligent and remove the clam from tank at night and giving it a thorough cleaning. Do not be afraid of removing your clams from the water,clams can survive to be airborne for hours at the time. Once you've taken your clam to the sink,look closely around the byssal opening and the edge of the top edge of the shell. This snails are equivalent of the vampire and will suck the life force out of your clams.If you'll depend on your wrasse only to do a job for you, you'll wake up to an empty shell in no time, FWIW.
I have to clean my Tridacna gigas almost daily to ensure their survival,the wrasse is still smiling btw.