I have to agree with dex. If it fits in their mouths, they will attempt to eat it. I didn't have trouble with trapdoors and my goldfish, but o the other hand, have been completely unsuccessful at establishing any population of pond or ramshorn snails. Despite numerous introductions of my bigger specimens, they tend to just disappear. Additionally, baby trapdoors never manifest either. I have not tried my pomacea with any of the goldies, as I am afraid to lose them.