They sometimes eat gelatinous zooplankton, such as hydra jellyfish and comb jellyfish. Both aquatic mothers and larvae of Hyaemedusa have stinging cells, which can capture prey and protect themselves. The prey will be caught by mucus and then sent to the gastric circulation cavity by cilia, and digestive enzymes will decompose food.
From digestive enzymes, we can know that they generally need carbohydrates, protein and lipids, but little is known about the vitamins and minerals they need. There are a large number of natural enemies in the sea moon jellyfish, including sunfish, leatherback turtle, Phacellophora camtschatica of Phaeophaga class and very large Victoria multi-tube luminous jellyfish. Sea moon jellyfish can also be eaten by seabirds. Some parasites also attack jellyfish.