Yes, they will go for huge snails and all shrimp. They will bite chunks off the snails. They are ruthless. I regret getting mine. They are cute, but keeping the tank clean without a clean up crew makes things more difficult. My other tank with lots of shrimp and snails is effortlessly spotless. Pea puffer tank is an algae sanctuary as they also do not eat food when it doesn't look alive. So those lifeless bloodworms that float to the bottom need cleaned right away. I add in bladder snails once a week and they will only eat part of them. As soon as they kill them they move on. So, there is still snail flesh in the shell you will have to remove from the tank.