Just visited Jenkinson's Aquarium and they still have the same Nautilus in a 55 Gal tank looks like a undergravel filter run by powerheads and I would think some other type of filtration. They keep it in a darkened tank. Most people would not even know he is there unless they read the signs.
Very few people keep nautilus in a home aquarium as they need a deep tank , chillers and they aren't too easy to care for. I only know one of our members L_S has kept a nautilus before, but it only lasted a couple of days. Do a search and see if you can find the thread, he had a few nice shots of it but i'm not sure if the images are still there.
apart from the requirements - why do you want one - not to be rude - but they really dont have any personality like other cephs as far as i have heard, i think a purpose built setup could house one if you did lots of research but what is the point!!! lol
arent they a threatened species anyway - i know you can get them but...