By Jason Scott, first published at Practical Fishkeeping (PFK) Website -- Authorized for use at in 2003.


Over the past twenty-five years or so I have kept a wide range of strange and unusual marine species, everything from Sharks and Rays to Frogfish and Flying Gurnards. In this time I have accumulated a good deal of knowledge about of how to care for the weirder aquarium inhabitants.

For many years keeping an Octopus had been a really appealing idea, I was fascinated to learn for myself if the stories regarding their intelligence and camouflage were true. I had heard rumours that they were extremely difficult to keep, but always ready for a challenge I decided to take the plunge.

The first problem I came across was a complete lack of information on keeping an Octopus in a home aquarium. I found lots of information about various species, but absolutely nothing about water conditions, filtration, aquarium size, behaviour and other crucial factors.

The first aquarium was fifteen gallons and equipped with a Bak-Pak skimmer with built in biological filter. An eight-watt fluorescent tube provided lighting, this was the smallest available, but still a little too bright. For decoration I used ten kilograms of live rock.

After the aquarium was matured I obtained a small Red Octopus, I later found out this was an extremely nocturnal species (Octopus bocki). Identifying any Octopus correctly is difficult, even for experts. This species only comes out in complete darkness and does not exhibit many of the character traits associated with other more day active Octopus, for example colour changes. It fed well on cockles still in their shell; it used the empty shells to form a barricade to its hole in the live rock where it lived. Any way this did well for two months, before it got stuck behind it's own barricade. It was trapped for several days before I realised, when it was released it was very distressed and died the next day.

Over the next few months I tried to keep Octopus in this aquarium on several occasions without success. They did well initially, but then stopped feeding and then deteriorated very quickly. I tested the water frequently and never found anything to be concerned about. Unfortunately I was not sure what the parameters for Octopus should be. In hindsight there may have been inadequate oxygenation/circulation or a low S.G. I had never been so unsuccessful in keeping any species before and Octopus were rapidly loosing their appeal due to my failures. I decided to throw everything I had at one last attempt...

I purchased a 36LX26HX20W custom built aquarium designed to house an Aquamedic Marin 500 internal filter, this includes a large air driven protein skimmer, trickle filter and a nitrate reactor. The Marin 500 is rated for aquariums up to one hundred and thirty gallons, I installed it on my forty gallon aquarium, this was to make sure inadequate filtration was not going to be an issue.

I wanted to be able to monitor water quality precisely twenty four hours a day this would give me the earliest possible warning that something was wrong. To do this I chose the IKS Aquastar and equipped it with pH, temperature and Oxygen probes. I also added an Air pressure sensor to assist in calibrating the oxygen probe and a redox probe to ensure correct functioning of the nitrate reactor. All the monitored water quality parameters are stored every hour and can be downloaded to a PC. The IKS unit also was set up to control the heater and the fifteen watt Gro-lux fluorescent light for use during the day and some tiny Red LED's for night lighting.

The aquarium is decorated with around fifty kilograms of well washed Tuffa Rock, I knew from previous experience that providing plenty of hiding places was essential. I also added some artificial corals and few pieces of marine safe plastic pipe, for the Octopus to explore.

Once all the equipment was in place any gaps around the sliding covers were filled with silicone to ensure it was escape proof. I also found a glass lock to enable me to lock the covers shut.

I filled the aquarium with reverse osmosis (R.O.) water and ran it for a few days, this was primarily to check everything worked OK as well as ensuring that the rock and pipe work would not leach any toxins. I was being ultra cautious this time round. Everything worked fine so the aquarium was drained and refilled with R.O. water and the salt added. Once the aquarium was up to temperature I added a bag of live aragonite mixed with coral sand to the base to give a substrate about one inch thick. The live aragonite matured the aquarium in just a few days.

Even for someone in my position (I work in the aquatics trade) obtaining an Octopus requires a bit of luck, they do not always travel well and it is hit and miss what species you may get. In the mean time I added a Domino Damsel to keep the filter ticking over. A few days later I visited Tropical Marine Centre, to my amazement they had single Octopus vulgaris with arms about five inches long. This was my lucky day, it was only the second time in many visits I had seen anything other than the commonly imported nocturnal species. I was aware that the aquarium had only just matured, but this was just too good an opportunity to miss, I had to have it.

Once I got home with my new purchase I tried to acclimatise it as is normally done with marine livestock. The Octopus had been in the bag for about five hours and was keen to leave as it climbed out of the bag after only a few minutes. It immediately went and hid at the very back of the aquarium where it could not be seen. The next evening a put a cockle in shell in for it to eat, and switched off the light. In the morning I was disappointed to find the cockle had not been touched. After this scenario had been repeated several times I was starting to get more than a little concerned. I knew healthy Octopus should have a voracious appetite. I wondered if the Domino Damsel was unsettling it, so the next night I decided to remove it. That night I tried a cockle once more, in the morning it had vanished, so at least I knew it was now eating.

Over the next week or so the Octopus started to come out more and more. The first time we saw each other, we were both startled, I jumped and the Octopus ejected a cloud of ink. This did not appear to cause any problems. I gradually increased feeding to three cockles per day, but nitrite rose to one part per million. I counteracted this by changing twenty-five percent of the water daily, reducing the feeding and adding a Polyfilter. Surprisingly the nitrite did not seem to bother the Octopus and much as it did me!

After two weeks the water quality was near perfect (NH4 0, NO2 0, NO3 0 PO4 0.01, pH 8.2, S.G. 1.025 and the Octopus was had already learned to associate me with feeding time.

This time it looked like I had finally succeeded, until... One night about 10:00pm it started act very odd like it was turning itself inside out! I was horrified, I immediately changed twenty-five percent of the water and added carbon. The next day it seemed OK. I never did find out what caused it to act so strange, but Octopus sometimes clean themselves by rubbing their body (mantle) with their arms, I was not aware of this at the time.

After this incident I decided to add some extra equipment and invested in a U/V sterilizer and chiller. The chiller is excellent, on all but the hottest days it keeps the temperature at exactly 25°C, With some of the exceptionally hot days we had this Summer I'm sure the Octopus would have really suffered without it. Since adding this equipment I have never seen the Octopus act out of character or clean itself.

Even with all the equipment I still change twenty five percent of the water & test it each week. I clean the protein skimmer & pre-filter daily. A Polyfilter is kept in the aquarium at all times as a precaution and replaced fortnightly. Even with all the water changes, I find phosphate still to be a problem unless I use Rowaphos. I have no problem with nitrate due to the high level of water changes and NO3reactor.

I have found Octopus to be every bit as intelligent as I had read. Everyone who has ever seen my Octopus do one of it's party tricks have never been anything less than astounded. Without doubt they require more time and effort than anything I have ever kept. But they are well worth the time and expense.

By the time you read this article I will have kept my Octopus for over six months and each arm is now eighteen inches. In this time it is has learnt many skills, it can open almost any sealed container and will even climb out of the water to take it's food from me. It still hides for much of the day, but is nearly always stuck on the front glass in the evening waiting for me to come home.

I consider I have finally been successful at keeping Octopus as in their natural life span is only one or two years at the most. I'm now looking to keep more challenging Cephalopods, maybe cuttlefish or even Nautilus, but they will need a bigger aquarium.

The difficulty of keeping Octopus and other Cephalopods is not to be underestimated; they certainly are not for the inexperienced. They require a good deal more expertise, equipment and dedication than many are prepared to provide.

Those who wish to learn more about Octopus should visit, I did not find this site until I had learned how to keep Octopus the hard way. Colin Dunlop is their expert on Octopus & Cuttlefish and has kept them several species successfully.

My Water quality
Ammonia0 ppm
Nitrite0 ppm
Nitrate0-5 ppm
Phosphate0.09ppm tested with highly accurate Merck kit
Oxygen90%+ of Saturation level
Temperaturestable at 25°C
Redox-100, Minus figure is required for correct functioning of the nitrate reactor.

Octopus facts
  1. Their brain is donut shaped with their stomach passing through the centre.
  2. They have excellent senses, especially vision, smell and touch, but they are thought to be deaf.
  3. A large proportion of the nervous system is in the eight sucker covered arms.
  4. Octopus have three hearts and Blue blood.
  5. Males die shortly after breeding; the females tend the eggs until they hatch, after which they also die.
  6. Even if they never breed natural lifespan is only One or maybe Two years depending on the species.
  7. Octopus have no bone structure, as they are invertebrates, despite this they are incredibly strong.
  8. They are amazingly intelligent and require mental stimulation in captivity to prevent them from becoming bored. (Not sure about this one)
  9. There are less than a handful of people in the U.K that keep them.
  10. They are best kept on their own, most tank mates make a tasty meal.
  11. Colour, texture and even body shape can be altered in an instant.
  12. They can squeeze through tiny gaps.
  13. Ink can be ejected to confuse would be predators.
  14. When swimming Octopus use jet propulsion, a bit like a jet ski.
Original publish date
Mar 1, 2003
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