Hi Sam, There are tropical species. Briarius is probably one of the most popular. But the problem with them is they aren't captive bred so when you get one you have no idea how old it is and may be near death. The octopus is a very short lived species, even in the wild, most only live a year or a few months longer. There are captive bred octo's for sell. Bimaculoides is the octo of choice for most. They are diurnal (active during the day and night) and require a temp in the low 70's which can be acheived in most cases by just not using a heater in the tank at all, and by strategically placing the tank in an area that is cool. They should be kept in a species only tank. Note that they are highly intelligent and are great problem solvers which leads to many octos escaping through small holes and even the overflows of tanks, so care should be used to escape proof the tank. For more info please come to tonmo.com. (The Octopus News Magazine Online)
Best of luck,
Spring