Upside-down jellyfish (Cassiopea andromeda) is found mainly in tropical waters, is a type of jellyfish with its tentacles facing up and its umbrella down. It has single-celled zooxanthellae in its body, and its tentacles are up to allow the zooxanthellae to photosynthesize and feed itself, and they only return to their downward tentacles when they move. But they don’t move very often, they stick to the walls of the tank, as you can see here. In addition, they are highly toxic, so try not to touch them.