Soft corals are animals that have flexible internal skeletons, unlike the rigid exoskeletons of hard coral varieties. Soft coral can often be seen billowing in the currents of the ocean, much like plant life. Soft corals protect themselves by stinging since they do not have a hard skeleton to defend against predators. There are several distinguishing characteristics that occur to soft coral when it dies, which makes it possible to identify it from live coral.
Observe the colour of the soft coral to see if it is completely white. A loss of pigment is a classic sign of dead coral in both hard and soft varieties. If the white sections are only on some parts of the coral, it is still alive, but sick. Once it turns completely white, the coral is dead.
Examine the ends of the coral to see if parts of it are see-through or translucent. This indicates that the tissue on the coral is dead. Although small translucent areas simply indicate disease or infestation by predators, once all of it turns translucent the soft coral is dead.
Look at the coral to see if it is limp and lying on the aquarium bottom. Watch the soft coral over the course of a day and see if it remains limp the entire time. Although soft coral will occasionally go limp, the ends will always become rigid again after a relatively short period of time. Corals that remain limp for 24 hours are dead.