Actually, most people come here thinking they are all the same and one person mentioned, "taking your pet out and playing with it"
. Everytime someone asks a question like this I have to do a brain dump to try to sum up what I think I have learned and hope for some feed back by others so here goes (note that I am only addressing the ones commonly kept, there are hundreds of others, some that appear to be abundant, would be nice to see in the trade but are not collected. There are two others that are collected but should not be and I do not include them in the list.):
Diurnals (day active species)
As a general rule, the Pacific
bimaculoides is likely the most desired for interaction traits and longevity. Unfortunately, it is illegal to catch and sell them in CA (but you can catch one for your own aquarium, eat them or use them for bait) and there are no known current captive breeders (viable with this species). If you were to locate one you will likely need a chiller. They can be kept at temps as high as 72 but 69 or below has shown greater longevity. I have not kept one of these animals and passed up the opportunity once because of the temperature requirements. Current members that are keeping them have caught them themselves.
An animal that often shows similar interaction characteristics is the Caribbean
hummelincki. This one can be legally sold and does not require the colder water but identifying it is problematic and almost no supplier will list them this way. It is also known as O.
filosis and the Caribbean Two Spot Octopus but none of the names will appear in a vendor's list. The best you can hope for is seeing a photo and noticing the eye spots or getting an octopus from Haiti. This is usually the species sold by SaltwaterFish.com when they have them. Often they are marked as a common brown octopus and occassionaly as
vulgaris but don't count on that as an ID. To add to the confusion, there appears to be two sizes (and I wonder if they are actually even the same species). The larger one seems to be far more interactive than the smaller, dwarf sized animal. I have kept 5 of this species, two of what I note as the larger, two of the smaller and currently have a young one (Monty) that I believe will be the smaller, less interactive kind.
Third on the high interaction, diurnal list is the Indonesian
aculeatus. This is a slighter animal than the Pacific (bimac) or Caribbean (hummelincki/filosis) two spot with long arms and a very sweet disposition. Unfortunately, most are full grown when they arrive and die of old age within a month or two. Live Aquaria will usually ship this species as their "Indonesian" octopus but the macropus noted below may be what you get when you order. I have not kept one of these for more than a week (I took an aging one from a keeper who was moving) but was going to try one when I got the second macropus noted below.
Next come the nocturnals or crepuscular (twilight/early morning hunters) animals.
The most commonly available and with mixed intereaction success is the O.
briareus. Arguably it is one of the the most beautiful of the octopuses when in full webover display. Most will learn to be active as early as 6:00 PM (feeding them at this time helps) but are the most active after dark. Interaction seems to be related to the size when they are acquired so the smaller the better but they are not as interactive as the afore mentioned diurnal animals. Most of the ones we keep are by-catch from crabbers in the Keys and one collector, Tom of TomsCaribbean, has been our regular supplier. If you happen to get a fertile female, it is possible (but very difficult) to attempt to raise some of the hatchlings (not viable with the hummelincki and a higher success potential with the bimac). I have kept 4 of these and have two hatchlings from Kooah that I am raising (Takanka and Cassy).
There is an Indonesian animal in the macropus family that I have had the pleasure of keeping twice (
Beldar and
Puddles). The animal appears to be very common (often spotted by divers) but the species is unclear (the common ID, O.
luteus, does not match the ID description). Unfortunately, this is a very nocturnal animal and unless you are up at 3:00 AM, you will not have much opportunity to experience interaction. It is most often acquired by ordering an Indonesian octopus from Live Aquaria and is the second most common shipped under that label.
Last in the nocturnal group is the dwarf O.
mercatoris. They can be kept in a tank as small as a 15 gallon with skimming and large weekly water changes, are relatively hardy and often available. Unfortunately they are very shy, very nocturnal and are often full adults when captured (often as by-catch from live rock collection but also found by crabbers). I have had a pair of tank hatched sibblings that would interact more than most but generally speaking, they avoid humans. If raised together (or found close together) and likely if they are introduced to a tank at the same time and are the same size, multiples can be kept in a single tank (we know of one bimac pairing but don't know if they lived successfully together through their adulthood). These are the easiest (but not easy) to successfully raise if you should acquire a fertile female and captive mating is quite viable. These are also one of Tom's by-catch finds and is often also sold by SealifeInc and CrammersCritters during crab season. This is the one species that is often labeled correctly by the Florida collectors or will be shown as
joubini. It is almost always labeled as a dwarf. I have raised a captive born and a captive bred generation of the mercs in addition to a couple of others, Sleazy being the last. I like to keep a merc in addition to my others as I find them charming but Monty is occupying that tank at the moment.
To see photos of each of these species and read personal keepers' journals go Forums->Journals and Photos and look at the top stickies. You will see a list of entries titled List of Our Octopuses 20xx. The lists contain the species and keepers. From 2008 forward, there is a link to the jounals for each animal.