Jellyfish eat a number of things in the World’s oceans. Plankton makes up most of their diet. During the day, jellyfish head down to deeper waters, as its safer for them. At night the jellyfish migrate upwards and feed on various kinds of plankton. Clear jellyfish, like the Moon Jellyfish, may take on the color of their food. Japanese Moon jellies are often found a dark purple, whereas Atlantic Moon Jellies are bright pink.
Jellyfish feed by swimming around and using their tentacles to net up plankton along the way. They do have some ability to detect food, but they often just bump into it. They feed slowly throughout a period of time