I know it sounds gross but crush them with your finger. Your fish and shrimp will eat them. You will have to physically remove them from your tank. Be diligent on removing edd masses too when you see them. I had assassin snails in all my breeder tanks. I'm pretty sure I had some in my shrimp tanks too but I can't say I ever noticed them attacking my shrimp. They were effective at keeping the snail populations at bay. Good luck to you! It can take a while to remove the from your tank but it can be done. I have used snail traps too and other foods they like. Let them collect and then gather them and toss them outside or in the trash. I had friends who ha chichlids who often would take my cursed snails and they would feed them to the fish. Also, remove all decorations from your tank and let them dry out for a day or two. It also helps kill the eggs that might be laid on them.