if you have a lot of pyramid snails here's what i would do...
-remove the clam(s) from the tank
-inspect each clam visually, focusing near the foot of the clams and any scutes on the clam's shell
-manually remove the snails with a toothbrush and or toothpicks (make sure to do this over a spare bucket and not the aquarium)
-siphon the sand in the area around the clam since some snails have surely fallen off
-repeat as much as possible, making sure the clam doesn't get stressed out too much
this, in my opinion is one of the better methods for pyramid snail removal.
i also want second what Jungle_John said:
QUOTE (Jungle_John)
but the best way to remove these snails is remove all regulare snails from the tank sence they feed on them, remove the clams to a place the p snails cant get to them (like a floating rack). and then just wait.
removing and quarantining the clam will help tremendously. you can manually remove the snails you see and let the others in the tank starve. but the only problem with this is the fact that the snails may survive longer than you choose to quarantine.
a coris wrasse will help, but the problem with using wrasses for pest control is that they don't get all of the pests, but merely help keep the population in check to some extent. a freshwater dip will knock off most/all of the snails, but i do not recommend a freshwater dip simply because the process is so stressful. the already stressed out clam may not do well during/after a freshwater dip.