Keeping Octopus in Aquaria: Lifespan, Escape-Proofing, Enrichment and Welfare

Octopus husbandry from research and public-aquarium sources: short lifespans and senescence, escape risk, copper and ink hazards, feeding, enrichment, venomous blue-ringed species and law.

A short-lived animal

Octopuses have short lives: up to about four years, and some species complete their life cycle in less than half a year. Most are semelparous. After mating, males become senescent and die; females lay a single clutch, brood it and then decline, a process triggered by the optic gland. In the giant Pacific octopus (Enteroctopus dofleini) the female guards her eggs for about five months, or up to ten months in colder Alaskan waters, before dying. Anyone keeping an octopus should therefore plan for a stay measured in months, and an animal bought as an adult may already be close to the end of its life.

Senescence

Senescence follows the single reproductive event and often comes just before death. In females it starts while brooding or soon after hatching, and in males usually after mating. A survey of public aquaria keeping giant Pacific octopuses describes senescent animals developing autophagy (self-directed arm damage), traumatic injuries and prolonged refusal of food. The same survey cites a review in which only about half of the octopus deaths examined were in mature, senescent animals, and notes that the clinical signs of senescence resemble those of disease, so a decline in a young animal warrants a veterinary workup rather than being assumed to be old age.

Escape-proofing

Even large octopuses can pass through a gap little more than 2.5 cm (1 in) across, and they often leave aquaria, sometimes entering neighbouring tanks in search of food. The tank needs a tight, secured lid, and every opening for plumbing, cables and overflows must be closed or screened. In a laboratory study of the California two-spot octopus (Octopus bimaculoides), each animal was housed alone in a 40-gallon tank with a separate sump, and each system was isolated from the others to prevent water contamination.

Water quality, copper and ink

The O. bimaculoides study kept water within ranges from long-standing cephalopod culture guidance: 15–20 °C, salinity 34–36 ppt, pH 7.7–8.2, ammonia and nitrite below 0.2 mg/L and nitrate below 100 mg/L. Coldwater species need more: public aquaria most often hold giant Pacific octopuses at about 10 °C, and facilities without a cold natural water supply use chillers. A review of cephalopod welfare stresses that these animals need strict monitoring of oxygen, pH, CO2, nitrogenous waste and salinity, and that poor water quality leads to infection, respiratory problems, agitation, repeated inking and jetting, and death.

Octopus blood carries oxygen with hemocyanin, a copper-based protein, and octopus tissues are naturally rich in copper. In an experiment on Amphioctopus fangsiao, continuous exposure to 50 µg/L copper reduced growth and feeding and damaged intestinal tissue, and acidified water made the damage worse. Copper-based fish treatments release dissolved copper on purpose and have no place in an octopus system. Ink is another hazard: if ink released in the tank is not removed, or the animal moved, it can coat the gills and cause asphyxiation.

Feeding

Wild octopuses eat crustaceans, bivalves, gastropods, fish and other cephalopods, including members of their own species. In the O. bimaculoides study the animals were fed live fiddler crabs or frozen-thawed shrimp. Public aquaria feeding giant Pacific octopuses reported frequencies from twice a day to twice a week, most often three to five times a week, with clams, shrimp, squid, capelin and crab the commonest items; every respondent who listed a diet used at least three food types. The survey notes there are no established nutritional guidelines, and appetite varies with life stage and temperature.

Enrichment and behaviour

Octopuses show short- and long-term memory, observational learning, tool use and play. Researchers describe enrichment as an important tool for countering the stress of captivity. In the O. bimaculoides study every tank had at least one den (a small flowerpot or ceramic cave), and some octopuses rearranged rock to build their own. Plastic building toys, shells and varied live prey such as snails and different crabs were rotated to prevent habituation, and shrimp were offered in a test tube whose cap was tightened step by step as each animal learned to open it. Several individuals then played with the cap, releasing it into the current and catching it again. Public aquaria report puzzle feeders and frozen food blocks as enrichment feeds.

Ethics and law

Octopuses kept in captivity are often wild-caught, as in the O. bimaculoides study, and their short life and high intelligence make them demanding to keep well. Their legal status mainly concerns research. Under EU Directive 2010/63/EU, research use of cephalopods from hatching onward has been regulated since 1 January 2013, including rules on taking animals from the wild and on staff competence. In the UK, the Animals (Scientific Procedures) Act 1986 defines a protected animal as any living vertebrate other than man and any living cephalopod, excluding embryonic forms. These instruments cover scientific use, not home aquaria; welfare laws in New Zealand, Canada and some Australian states also recognise cephalopods. Verify current status and the rules that apply where the animal is kept.

Rearing octopus from eggs is covered in the octopus breeding guides. Related marine guides cover coldwater tidepool tanks and jellyfish kreisels.