Archie is 12 and active --walks with us every day --loves to play ball. I noticed this black stool a couple of days ago and thought it might go away. He still has his usual appetite:however I think it might be wise to feed the rice and boiled chicken. He may have eaten something similar to one of the testimonials I read on your site. If you have any suggestions before I am able to visit his long time veterinarian, I would appreciate it.