I have a golden mystery snail also, I named it Crust ;-] I gave him some cucumber today and he didn't seem to even notice it. I'll leave it over night but I'll take it out tomorrow and replace it with some kale if he doesn't start munching on it. I hope your new snails work out! :)
I have 2 mystery snails.. I put some kale in but the dang stuff floated so I am trying to find things I could spear the kale with and poke into the gravel. I have read snails are sensitive to metals...would a wire hanger (for clothes) work? Or does anyone think it's got bad stuff in it that'd leech out and hurt Crust and Fast Eddie?