VERY DIFFICULT. I've had them in a few times in the past and won't get them in unless someone asks and knows about them. I don't know of anyone that has any long term success with them. Most end up dying over the course of a month on a good run.
Difficult is true I have had them and pinecone fish and they are harder to keep than the pinecone. This is mainly because of the temp they live in most of the time, they are deep water fish and come closer to the surface only to feed. good luck if you decide to keep one.