My friend has an upside down jelly in his refugium. It is about a year old and it basically pulses on the bottom. He doesn't do anything for it. I dont know if its healthy or even happy. My friend that owns a fish store says they need a tank with no sides and low light. Then they float around in it like riding the tides. He says they are very hard to keep unless you do like innovator said with the feeding. Not to mention getting stung!
No, I do not personally keep jellies; however, my coworker is what I consider an "expert" who has great experience professionally culturing various species and I feed off of her knowledge. The only jellies I have limited hands-on experience with are Aurelia i.e. Moon jellies. Either way, they can be quite durable and easily cultured if properly cared for, as in all things. The book I linked is a fantastic source for beginners.