California two-spot octopus (Octopus bimaculoides) care guide

Group
Other invertebrates
Other names
Two-spot octopus, Bimac octopus, Bimac
Family
Octopodidae
Origin
Eastern Pacific along central and southern California and the west coast of Baja California, Mexico, from the shore to at least 20 m
Water
saltwater
Maximum size
75 cm
Temperature
15–22°C
pH
8–8.4
Hardness
SG 1.024–1.026
Minimum tank
300 litres
Care level
expert
Temperament
aggressive
Reef safe
no
Lifespan
1–2 years

Care

The California two-spot octopus, or bimac, is a medium-sized octopus from the coast of California and Baja California. Its mantle reaches about 17.5 cm and its arms about 58 cm. It is named for the two false eyespots, one below each eye: a shimmering blue ring set in a black circle. It is usually grey with yellow blotches but can change colour and texture rapidly. In 2015 it became the first octopus to have its full genome sequenced. Welfare: Cephalopods are short-lived animals that need expert care, a secure, tightly fitting lid and a dedicated tank of their own. Octopuses and other cephalopods are recognised as sentient animals under the Animal Welfare (Sentience) Act 2022. Bimacs show distinct personalities from a few weeks old, play-like behaviour and problem-solving, so they need daily enrichment. Set-up: a dedicated tank of 300 litres or more with no tankmates, plenty of caves and rubble for dens, and a heavy, locked lid with every gap sealed; octopuses escape through very small openings and die out of water. As a temperate species it does best in cool water, preferring about 18–22 °C (15–26 °C reported), so a chiller is usually needed. Use a large protein skimmer and strong filtration, because octopuses produce a lot of waste and release ink when stressed, which can poison the water. Keep water quality excellent and stable. Lifespan: even with perfect care it lives only about one to two years, and dies after breeding. Buyers should understand this before taking one on. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most other invertebrates. Never treat a tank holding them with copper, check the label of any fertiliser or medicine, and keep nets and buckets used for copper-treated tanks separate. Sources: Wikipedia (en.wikipedia.org/wiki/Octopusbimaculoides). Checked October 2026.

Diet

A nocturnal predator. Hatchlings eat amphipods and mysid shrimp; adults eat crabs, shrimp, molluscs and fish. In captivity feed live or thawed crabs, shrimp, clams, mussels and fish pieces, and use puzzle feeders such as jars for enrichment.

Breeding

It breeds once and then dies. Males pass sperm packets to the female with a modified arm and die soon after. The female lays 20–100 large eggs in her den, guards them and blows water over them for about five to seven months without eating, and usually dies after they hatch. The young hatch as small, well-developed octopuses that can hunt straight away, so rearing is possible for experts, but they need a steady supply of small live food.

Compatibility and tank mates

Keep alone in its own tank. It eats crabs, shrimp, snails, clams and fish, and may be injured by or injure other animals. Not suitable for reef or community tanks.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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