Depending on the room you have, a sump with a filter sock is better than a canister filter for an octopus tank, more because the sump will accommodate all the things you don't want in the display (skimmer - VERY HIGHLY RECOMMENDED, ESPECIALLY FOR INK, filter, heater - you don't want this where the octopus can touch it as they don't understand heat and burns) and to make it easier to make the tank escape proof. An octopus can squeeze through any opening that is the size of its eye (the actual restriction is the beak but you can't see that and the eye will be roughtly the same size).
I am afraid you will not find an octopus breeder for octopuses of any species. There was an attempt at providing captive bred and raised bimaculoides about 10 years ago but the company failed and an educational facility that also did some limited bimac breeding (possibly O. mercatoris as well) that is also defunct. Currently there is a small breeder for cuttlefish that can be purchased through Live Aquaria and that is about it for Cephs. Your best bet for sourcing
A. aculeatus will be Live Aquaria when the have Indonesian animals in stock. These are most often
Abdopus but not always
aculeatus and occasionally a medium sized (about the same size as
aculeatus but very nocturnal)
Macropus.
There has been NO success raising A. aculeatus from hatchling to adult (21 days is the longest survival I know of) so this species is strickly wild caught. On a rare occasion member have been successful with a few O. mercatoris and O. briareus (very few with the later) but survivors are few and far between and not in the commercial arena. The difference in any success is the first month of the lives of the hatchlings. A. aculeatus is a "small egg" species and the new hatchlings spend a month or so as pelagic animals swimming in the plankton before settling. The animals where we do see success are "large egged" and the hatchlings become benthic in the first day.
There is a collection of links to extended information posts for new octopus keeper assembled in the Octopus Care forum in the sticky
Posts with Info for New Octo Keepers that should help with some of the questions you have asked and a number you have not yet known to ask
. One post lists the most commonly kept species and gives a thumbnail sketch about each one. Be sure to read the part about the "box of chocolates".
The animals we can keep in a home aquarium do not appear to be quite as mentally robust as the Giant Pacific Octopuses displayed in most public aquariums though O. vulgaris may be close (but not easily found) and most medium sized species can learn to unscrew a jar lid but few will entertain themselves with "toys" (note that each animal is different so there is some variation and mine have made a liar out of me more than once). Many will become interactive if you are willing to spend a lot of time with them (often just sitting in front of an apparent empty tank). You will get a better idea of how different species act/interact by reading through some of the journals. There is a set of stickies at the top of the Journals forum titled List of our octopuses with the different years listed. The more recent years have links to the journals.