Octopus & Squid

Ammonia poisoning

SignsBody fades to white, fast labored breathing, arms curled in and sluggish response, more mucus

PreventionFully cycled large filter and big water changes. Keep ammonia and nitrite at zero at all times and test daily

Oxygen deprivation

SignsMantle opens and closes fast and shallow, limp near the surface, body white, arms spread and motionless

PreventionBlood carries oxygen poorly. Strong aeration and a skimmer; keep the water on the cool side to hold dissolved oxygen

Skin ulcers / infection

SignsWhite patches or holes in the skin, arm tips dissolving, suckers falling off, cotton-like growth on the body

PreventionCaused by poor water quality and abrasions. Layout with no sharp edges, keep nitrate low, water change at least weekly

Autotomy / self-eating (stress)

SignsBites and eats its own arms, arm tips missing, stays hidden in the den, disordered coloring

PreventionProvide several hides and keep lighting dim. No tankmates, and do not handle often

Senescence (post-spawning decline)

SignsEats nothing at all after spawning, fades to white, arms hang limp and skin peels

PreventionNatural end of life with no treatment. Choose a small young animal at purchase and know its lifespan

Copper / medication poisoning

SignsSuddenly thrashes about after medication is added, inks, goes limp and white, dies within a short time

PreventionCopper-based fish medications such as ich treatments are lethal. No disinfectants either. Never add any medication; fix water quality instead

Arm damage / loss

PreventionCover filter intakes and pumps. No sharp rock or shell fragments in the tank

First aidArms regenerate. Do not apply medication; keep the water clean and increase water changes to prevent infection. Consult a vet if the wound dissolves and spreads

Drying out after escape

PreventionSeal the lid and secure it with weights and tape. Block cable openings, overflows and drains too

First aidAs soon as found, return it to the tank with wet hands. Even if the skin is dry, put it back and watch. Increase aeration

Suffocation by ink

PreventionDo not startle it. Avoid sudden lights or tapping the tank, and keep plenty of water volume

First aidImmediately change half or more of the water and add activated carbon to the filter. Maximum aeration. Ink clogs the gills, so act fast

Squid wall collisions

PreventionSquid jet straight back into walls. Use a round or edgeless large tank with a black back panel so they see the wall

First aidMantle-tip wounds heal poorly. Dim the lights, keep quiet and do not startle it. Consult a vet if it stops eating

Octopus bite (venom)

RouteBeak bite injects venomous saliva

PreventionDo not lift it with bare hands. If bitten, rinse under running water; seek medical care if swelling or numbness develops

Tetrodotoxin

RouteBlue-ringed octopus bite. Also poisonous if eaten

PreventionNever touch a small octopus with blue rings. If bitten, call 119 (ambulance). Do not eat kept animals either

Vibrio infection

RouteSeawater or raw food touching a cut on the hand

PreventionDo not put a hand with cuts in the water. Wash with soap after working; immunocompromised people wear gloves

Nontuberculous mycobacterial infection

RouteCuts from tank water or decor become infected

PreventionWear gloves when working. If a red lump on the hand persists, see a dermatologist and mention aquarium keeping

Food

• Common octopus: live crabs, shrimp, shellfish. Once settled it also takes thawed shrimp
• Bobtail squid need live small shrimp. Once a day, only as much as is eaten
• Growing animals daily, adults every 2 days. Always remove leftovers the next morning

Water

• Artificial seawater at specific gravity 1.022–1.025; water changes at the same gravity and temperature
• Ammonia and nitrite zero, nitrate low. Change one third twice a week

Toys & play

• Enrichment: put shrimp in a lidded jar and let it open it
• Add movable items such as PVC pipe and shells so it can build a den
• For bobtail squid, fine sand to bury in and chasing small shrimp is their play

Nest, bed & hideout

• For octopus, several unglazed clay pots or PVC pipes the whole body fits into
• For bobtail squid, fine sand at least 5 cm deep to bury in by day

Bedding & litter

• Octopus: edgeless coral sand or bare bottom. It digs with its arms, so do not fix it in place
• Bobtail squid: fine-grain sand. Coarse sand damages the skin
• Remove food shells and remains daily so dirt does not build up in the sand

Cage / housing material

Glass tank with a heavy, sealable lid. Chiller, skimmer and large filter

Size & space

200 L or more of seawater per common octopus. Bobtail squid: 1–2 in a 60 cm tank

Layout

• Block every lid gap, cable opening and drain, and weigh the lid down
• Cover pump intakes and heaters. Remove corners and sharp objects
• Place several hides; keep lighting dim and the photoperiod short

Placement notes

• Mount power outlets above the tank so water cannot drip down from around the lid
• Avoid direct sunlight and keep a chiller installed for temperature spikes

Exercise, free-roam & walks

• No walks needed. Crawling and exploring at night is its exercise
• Use puzzle feeders for stimulation and to prevent boredom
• Coming out by day and crawling the walls nonstop signals an escape attempt; check the lid

Temperature & humidity

TemperatureCommon octopus 15–24°C, bobtail squid 20–25°C. Above 28°C is dangerous

HumidityNo humidity control needed. Evaporation raises gravity, so top up with fresh water

Summer & winter

• Summer: a tank chiller is essential. In a power outage, cool with frozen plastic bottles
• Winter: avoid sudden cold; change temperature gradually. Battery air pump for outages

Nail trimming

Instead of nail trimming, check the beak and suckers. Confirm it can crack food shells and that no suckers are falling off

Brushing, skin & coat care

Do not touch; observe skin color and texture daily. Fading to white or ulcers signal poor water quality

Other care

Use a hydrometer, thermometer and ammonia test daily; check the lid fastening and cable openings every day

Protection from predators

• Use a locking or heavy lid so cats and children cannot open it
• No housing with fish or crabs. They prey on each other
• Squid hit the walls at noises and vibration, so place the tank somewhere quiet

Foreign-body ingestion

It grabs and bites heater fragments and small decor parts. Use only unbreakable items in the tank and no small parts that stick to suckers

Being stepped on

An escaped animal can be stepped on or dry out unnoticed. If the floor or area around the lid is wet, search the surroundings and behind furniture

Getting pinched

Arms get sucked into pumps or overflow pipes. Fit fine-mesh covers on intakes, and open and close the lid carefully so no arm is caught

Falls

Heavy rock in the tank can collapse and pin it. Glue rocks in place or use rocks too heavy for it to move. Check that the stand is earthquake-secure

Escape

If the beak fits through, it gets out. Seal the lid with weights and a lock, and block cable openings. If it escapes, search behind furniture and drains and return it with wet hands

Safe release procedure

1. Keep your hand still underwater and wait for the beak to release
2. Gently peel off the suckers one at a time underwater, starting from the base of the arm
3. Once free, release it quietly toward its hide without startling it
4. Rinse the bite under running water; seek medical care for swelling or numbness

After the release

Rinse and disinfect the bite. If swelling, numbness or breathing discomfort develops, see a doctor immediately and say it was a bite from a marine animal

What to tell the vet & what to bring

Species, time kept, temperature, specific gravity, ammonia and other water readings, diet, medication history, any inking or escape. Bring tank water

Checking consciousness, breathing & heartbeat

• Is the mantle opening/closing (breathing) slow and regular, or fast and shallow?
• Does it pull an arm in when touched, do the pupils respond, does the color change?
• Lying on its side, white with no color return and suckers not gripping is critical

Stopping bleeding

• Blood is blue, so bleeding is hard to see. Arm wounds stop bleeding in clean water
• Do not use medication or disinfectant; reduce bacteria with water changes
• If bleeding continues or the wound dissolves and spreads, see a vet who treats marine animals

Transport

• Place it in a lidded container with its own tank water and tape the lid shut
• Keep cool in a foam box, dark, without shaking, and travel quickly