Ah! That makes more sense, then. Large snail, new tank, and not much to eat.
If the flakes can sit on the bottom, or on rock, that would work, too, since the snail can't chase it around. I know my lfs has sheets of seaweed that they make themselves, it's a mixture of things. But this is their own brand....you might check with your lfs, see what they have. Plain ol dried seaweed from the asian market doesn't seem to sit well with my tankmates, but a snail might like it.