DSB, clams and pyramid snails

[Donovan]

I have an infestation of snails and the DSB has to come out. The tank is 240 gallons with 15 clams. I have lost several the last few months to the snails and have been fighting them for too long. I sucked out a 6 inch square from the top layer of sand and sifted through it. Here is a pic of just some of them that i pulled out.

I have thousands of them in my sand bed and are taking over the tank and killing my clams. I have no choice but to suck out the entire sand bed...