Sometimes a newly introduced coral just doesn’t do well. It doesn’t adapt well to the intense lighting, or the chemical balance in the aquarium just isn’t a suitable environment to the coral’s health. Even a coral that has been in the system may take a turn for the worse if even the slightest change is made. Regardless, the coral dies off, often rapidly, and only the slightest bit of tissue and polyps remain. Fortunately, if even one polyp remains from the severely affected coral, it could make a comeback. Of course, the water parameters that caused the die off would have to dramatically improve for this to happen, but it can happen.