It depends on the fish, it depends on your tank set up, etc, etc, etc.
They are typically found in a specialized habitat and can work, for example, in a strongly lit refugium. Would I say that yes, you can generally keep them in most of our tanks, no...they are not for most hobbyists and most tanks I'm afraid. They are not as difficult as other types of jellies...then again, they are also not as interesting, IMO, as other types of jellies.