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I haven't had luck with mine eating ones that are that big. I got yoyos because they were cool looking (and now have doubled in size!) and fit into my "India" tank, and I figured I could feed them some of the brown ramshorns that were multiplying in a guppy tank, but I have never actually seen them eat any snails. I have about 5-6 nickle sized ones in there and maybe 2-3 smaller ones, so I figure they are taking care of the little ones that I never even see.
So, IME, no, they don't eat the larger ones, but they will take care of most of the smaller ones that come from the big ones! =) HTH