Jellyfish appear to glow in an aquarium because of the way their translucent bodies scatter light.
Although jellyfish often appear to glow in an aquarium, this is only because their translucent tissue disperses and colorizes light to make it look like they are glowing jellyfish. Indeed, jellyfish look magnificent under the right lighting but they do not produce their own light.
The key to making jellies look their best is balancing strong spotlights with a soft back light. Often the back of a jellyfish aquarium will be lit through a translucent blue background that fades to black at the bottom of the tank to give the illusion that the jellies are floating in the open ocean. Lighting is one of the most important factors in making an attractive jellyfish aquarium and it takes experience to get it right.
There is one species of jellyfish that can glow in the dark by producing its own light. The crystal jellyfish (Aequorea sp.) has two molecules, aequorin and green fluorescent protein, that enable it to emit flashes of green light. Green fluorescent protein is used in cellular research to label and track biological processes that occur on a very small scale that would otherwise be difficult to quantify. Drs. Osamu Shimomura, Martin Chalfie and Roger Tsien were awarded the 2008 Nobel Prize in Chemsity for their work discovering and using green fluorescent protein.
Color-changing lights can be installed on our aquariums to make the jellyfish change colors. White moon jellies will pick up whatever color of light is shone upon them and glow with that color, as shown in the video below.
