He can eat them and a little should not cause much harm, but they are not the best thing in the world for him. To much could over load his system and even cause a "bloom" of worms. For Russians ideally you stick with weeds, greens, flower blooms, certain leaves, and even some Mazuri. Everything given in a variety of one type (or several even if you wish) at one time and then something else when that item is gone.