Jellyfish require very large aquariums to thrive for any length of time with the averages ranging from 800 to 2000 gallons, though some species can be kept in 200 gallon tanks. Different species cannot be kept together, and you cannot keep any other species of anything in the same tank. Most species require you to add a refridgeration unit to chill the water, depending on the species 50 to 70 degrees, with a few that will live in 80 degree water, though cooler is better with them. The very critical thing is that thier aquarium have alot of water flow through filtration which would amount to a very large wet/dry filter, an oversized protein skimmer, then the chiller, then through a resin absorbtion unit and a calcium reactor. Once the water goes into the tank (which needs to be modified so the corners are curved preferably) the water current needs to go in a steady and consistant manner completely through the tank and attention paid to the flow over the bottom surface. As long as you can maintain the jellies in suspension they won't fall apart. Water must be screened and skimmed as it exits the tank with a pass-by flow aross the exit screen to avoid filtering out the jellyfish.
...especially considering that you are limited to very small species of jellies which can be hard to obtain. Many of the more popular species like Chrysaora fuscescens and other colorful species get way too long to fit in those, and what happens is the jellies get tumbled and wrapped up in thier own tentacles as in a washing machine.....