Someone recently gifted me with a tank from JellyfishArt.com -- a desktop tank, along with two small and one large jellyfish.
I was a little skeptical at first, but I've had them for nearly a month with no problems. I looked up the pricing, and it looks like my gift cost less than $400 -- it came with all the required supplies, as well as a 6-month supply of frozen plankton.
The cylindrical tank and the filter work together to keep the jellies in motion. A remote-controlled LED provides a variety of colors, but I tend to favor the simple white light. If you're curious about keeping these non-stinging jellyfish as pets, I suggest checking out Jellyfishart.com. They also have a number of instructional videos that demystify the acclimation and feeding process. I've never even had a goldfish, but so far, these jellyfish are thriving.