The three I sent off for necropsy that had blackhead had negative fecals, so just remember a negative fecal just means that no worms eggs were found in that poop, it does not mean that they don't have worms. And from what I recall about your previous worming posts, you don't worm orally, or am I thinking of someone esle? Anyway, if you want to rule out worms, now might be a good time to give him Safeguard for five days. My big boys get 3ml for five days.