Did you know that corals poop? Just like anything else that eats, there is bound to be some metabolic byproducts created by corals, and they have to be dealt with somehow. Because corals only have one opening, they essentially eat and poop out of what can only be described as their mouths. For many new hobbyists, this site can be something of a shock. During the pooping process, the coral usually deflates or takes on sort of an odd appearance, with small strings of dark (usually black) stuff coming out of their mouths. This usually leads aquarists to think their corals are dying, which prompts many questions and comments on aquarium forums and social media sites. But, as the saying goes, everybody poops, and coral pooping is a perfectly normal behavior. The process is short-lived and the coral usually finishes the entire process within a couple of hours at most.