For the last time, people, let's get it right: whether they're living or dead or made into lamps that glow in the dark, jellyfish are not fish. They're jellies, or gelatinous zooplankton, if you prefer. Thank you for your kind attention to the finer points of cnidariology and modern home decor.
The thing about fish, you see, is that fish are vertebrates. They have spines. Jellies, on the other hand, are not only spineless, but in fact completely lacking in bones at all. They're just goo. You could spread them on toast if you wanted to. Or, you could breed them, wait until they die of natural causes, flash-freeze them in liquid nitrogen, cover them in epoxy resin, and turn them into these phosphorescent lamps that will glow in the dark.
Many species of jellies contain bioluminescent proteins that allow them to absorb light and re-emit it, causing them to glow in the dark. In fact, most of the glowing animals that we've met are using jelly proteins to pull it off. The jellies in these lamps may be, you know, dead, but those proteins are still hard at work, and they'll store up light during the day and glow softly at night. Each lamp is unique, and there are several different sizes and species to choose from, starting at a mere $35 and ranging up to $170.
Editor's Note: Evan Ackerman, being a damn scientist, sir, would like to make it known that he formally objects to "jellyfish" being in the headline of this article for the reasons expounded upon above. (He originally had "jellies.") His objection has been noted, ridiculed and overruled.
Update: Since we published this article, the Amazing Jellyfish website has changed and no longer says that these are real jellies that have been frozen in liquid nitrogen and cast in epoxy (although you can still find the reference in Google's cache). Looks like these may be fakes: still pretty, but far less cool.