I would like to have a chambered nautilus tank, except for the cold water thing. They are really nice critters.

But octopera (my preference for the plural, for no good reason) are nice too. They are really intelligent. About as smart as a dog I hear, and way smarter than cats. Someone at some research school somewhrer trained them to open ball jars. And they got really excited when you screwed the lids on too tight. Flashed all their colors as they tried their best to open them.