It's tough blue_eyes.. Once when I had pyramids (and no clams) I tried to manually remove them from the snails daily... but it became an overwhelming task to say the least. They lay eggs so multiple generations are inevitible. I eventually let the reef go snail-less for several months (starved out the pyramids) before trying to introduce any snails/clams. I can happily say that my reef is pyramid free!! 
NOTE: the preferred host of a pyramid is a clam...second are certain snails. Astrea snails are what I found them feasting on.
NOTE: the preferred host of a pyramid is a clam...second are certain snails. Astrea snails are what I found them feasting on.