The main deciding factor if you are considering getting an octopus, is usually the lifespan. At 1-2 years, it is rather short, and an even shorter 6-8 months for Dwarfs/Pygmies. Tragically short, considering the wonderful nature of these creatures. The worst part about purchasing a wild-caught octopus is that you don’t know how old it is. It might be a few weeks from death when it arrives. It might be a young juvenile with many joyful months to go. Unfortunately, very often new owners find that their new octopus has made a den, laid eggs, and won’t see it out again until they are taking its carcass out of the tank, then they can try their luck at raising the babies... if the eggs are fertile.
Next you have to consider that there really aren’t any suitable tankmates. And even still, whether or not you can provide suitable live food if it never accepts frozen foods. Also, a chiller may be neccessary as some species are from cold water areas. If that isn’t discouraging, then please continue reading.
Before I get started on the needs of a captive octopus, let me emphasize that Blue-Rings are deadly. This is not a myth. It is not over-hyped. It is REAL. It bites you, YOU DIE. It’s not a quick, peaceful death either. You lay there. Your brain and your heart are the only organs that continue to function unaffected, while you suffocate to death, hearing and seeing everything going on around you, unable to do anything about it. Not pleasant at all.
Mimic Octopus, Zebra Octopus, or Wonderpus are very rare finds in the wild. There is very little information about them available to hobbyists, and they are quite different from most other octopus species. There are very reputable, responsible people keeping these particular species with mixed results. They do not display their amazing mimic behaviors in captivity. That said, with conservation in mind, let’s stick to the more common species, and leave the rare ones in the ocean where they belong. Besides, why spend $300-$600 on something that might possibly die in a week or two?
Most octopus species share the same basic care neccessities: Strong filtration, low lighting, and live food items of saltwater origin.
An ideal tank size is 50 gallons or more for most common species, 30 gallons for a “Dwarf” or “Pygmy”, and 125 gallons for an O. Vulgaris.
Acclimation:
I am personally a fan of the drip method. A 5-gallon bucket and a “Critter Keeper” is good to have for this occasion. Why the Critter Keeper? Because your octopus is likely to climb straight out of the bucket/bag during the acclimation process, so keeping it contained is a good idea. After enough water has filled the bucket to submerge the Critter Keeper, allow the octopus to come out. This is a great time to bond with your new pet and get an idea of its personality. Some octos are bold, and some are shy. If you’re brave enough, try touching it and see what its reaction is. Not too much interaction yet though! You don’t want to stress it out after itsjourney, and you definitely don’t want to make it ink! This could be disastrous!
Filtration:
Octopuses are very messy eaters. While they munch down on whatever meal they picked up, they discard a lot of it. Pieces are torn and spit out. Then, during digestion, more pieces are ejected. Considering most of your cleanup crew are going to become snacks, the buildup of waste in your tank is inevitable. Thus, it is wise to have way more filtration than necessary running at all times. If you have a 50 gallon tank, you should have a skimmer designed for a 150. Wet/Dry filters are an excellent method of denitrification, as are refugiums. This means plumbing! An internal overflow is idea, but it can be done in a tank that isn’t drilled. As with all saltwater tanks, regular water changes are mandatory.
An abundance of Live Rock is suggested, as it would be for any saltwater tank. You just can’t beat its filtration abilities. The more rock you have, the more hiding places your octopus has. This will make your octopus feel safer, and in turn, it will be more likely to venture about its home in full view.
Housing:
Octopuses are very inquisitive creatures. It is going to explore every single inch of its habitat. This includes the intakes and returns from your filtration. You can use plastic mesh/window screen to cover the intakes so that your 8-legged buddy doesn’t get sucked into a propeller, pump, or overflow. It is also wise to fasten the protective cover on any powerhead intakes securely, using non-toxic glue, perhaps even using foam/sponge to keep the tips of its arms from being sucked into the propeller. Next, ALL POSSIBLE EXITS must be covered and sealed. Any gaps between the lids and equipment should be closed off with whatever non-toxic material you deem fit. I have found that thick styrofoam is great for filling large spaces, and is easily cut to fit, and can be squeezed into place to make a secure bond. Duct tape also lives up to its reputation. Oh yeah, and tape those lids down tight! After watching you open and close that lid a few times, your octopus is going to try to do it too.
The main thing to keep in mind when octo-proofing your tank, is that the octopus has no bones. It can squeeze through any tiny space as large as its beak if it really wants to. This might be easier to gauge by its eyes, since the beak is hidden 99% of the time.
Lighting:
Many Octopus species are nocturnal and thus react poorly to the typical reef lighting. Low-wattage fluorescent bulbs are ideal, and with time, a nocturnal octopus may adapt to daytime activity. If not, keeping the tank in a dark room, with red lighting might do the trick. Octopus's eyes do not pick up frequencies of light in the red range very well, and therefore tricks them into thinking it’s still dark. Even a diurnal octopus may react poorly to metal halides or VHO lighting. The higher the kelvin rating, the more likely it will drive your octopus into hiding.
Feeding:
The octopus is a saltwater predator, therefore it is designed to eat saltwater prey. Food items of freshwater origin are not fit for the octopus diet, or any other saltwater predators diet for that matter. In order to sustain a healthy specimen, one should feed live crabs, shrimp, snails, mussels, and perhaps even small fish. Offering frozen shrimp or silversides occasionally could lead to the animal accepting a more convenient and cheaper food source.
On a side note, foods for filter feeders may actually benefit octopuses too, but there is no scientific data to back this up.
Tankmates:
Depending on your octopus's personality, it may or may not be compatible with a potential tankmate. Most fish are prone to nipping at anything they perceive to be edible, and an octopus in disguise might appear to be some tasty algae, or an arm might appear to be a squirmy worm. This harassment might lead to stress, which could result in your octopus hiding all the time, or even its death. On the other hand, your octopus might be a fish-eating machine and decimate the population of the tank very quickly. Either way, it’s safest to avoid either of these scenarios.
The safest choice for a tankmate seems to be starfish and/or urchins -- Serpent Stars, Brittle Stars, Chocolate Chip Stars, etc. Keep in mind however, that some starfish are voracious carnivores, and if your octopus gets trapped in a hole with the starfish on top, it will likely become starfish dinner. Also, some urchins have venomous
spines and octopus flesh isn’t very protective.
Entertainment:
Not your entertainment, the octopus's! Being an intelligent creature, the octopus needs mental stimulation to live a healthy life. Octopuses are proven to display “play” behavior, and need something more than just rocks and shells to play with. They need challenges. They need toys!
Adding non-toxic toddler toys to your tank is a great way to discover just how creative an octopus can be. Try a ping-pong ball, a bottle, a container with snap on lid, or Legos. Place a crab in a small, clear container with a lid, and it’s not unlikely that your Octopus will eventually figure out how to remove the lid for the treat inside.
Senescence:
Senescence is the period in which the octopus begins to deteriorate. This is usually brought on by old age. Symptoms may be shown by cloudy eyes, or strange behavior. Male octopuses are reported to actually become senile. Most females are laying eggs at this point, and will most likely refuse to eat and remain with the eggs in her den until death.
Reproduction:
Reproduction is the beginning of the end for most octopuses. Males will die shortly after mating, and most likely females will die shortly before, or during her eggs hatching. Rarely females can live weeks after her eggs have hatched. Fortunately for females, they can choose when to lay the eggs, so they can live months after receiving the male's donation.
Eggs:
Octopus eggs are comparable in appearance to grains of rice. Usually they are strung together in groups, hung from the ceiling of the den. Some species hatch as tiny octopuses, some hatch as even smaller plankton-sized individuals. I personally am not experienced in this particular area, but there are people currently successfully breeding octopuses, so it can be done!
Most local fish stores have no idea what they have when they receive an octopus. All too often they are labeled “Common Octopus” or even just plain “Octopus”. This is a problem, because it could be a Dwarf, or it could grow to be a significantly large O. vulgaris. This will impact the size of tank, the filtration of the tank, and the amount of food it needs.
If you’re seriously interested in purchasing an octopus, it’s best to do tons of research. Read, read, and read some more. Look at octopus pictures and familiarize yourself with the identifying features of individual species. Some have extensive webbing between their arms, some have little webbing, some have really long arms, some have really short arms, some have false-eye spots. Coloration and pattern may give you an idea, but isn’t a reliable way to identify a species, as it changes from moment to moment.
O. Briareus for example show a bright blue/green shine and have very extensive webbing. Dwarfs have very large eyes in relation to their mantle size. Aculeatus abdopus has very long arms. O. bimaculatus and O. bimaculoides, as well as O. filosus aka O. hummelincki, have a false-eye spot below their eyes which flashes a bright blue when distressed.