No, I would not leave them in there as if they eat to much vitamins they can over dose on the fat soluable one's. I would just dust your feeders with the vitamins two times a week. If you have trouble getting the vitamin powder to stick to the meal worms you can lightly mist the meal worms with water and the vitamin powder will stick then or you can use a damp paper towel and get the meal worms wet that way. Also, Repashy makes a vitamin formula for leos that is really good and sticks really well.