This is a 100% way to get rid of them. first take one of the snails and dip it in white spirit and pop it back in the tank.(this will not harm your fish due to pigaments in their skin)this snail now carrys Sn3 a very toxic poison .when this snail mates with the female of the speaciese it will fetilise the poison into its eggs and the eggs will not produce and eventually float to the tops then you simply scoop them out keep doing this till they stop breeding.i have tryed this over 50 times and this has worked not a single fish of mine has died during this.