Eel

White spot disease (ich)

SignsWhite spots on body or fins, rubbing against the bottom or walls, faster gill-cover movement

PreventionAvoid sudden temperature changes. Quarantine new fish and plants in a separate tank for 2 weeks before adding

Cotton wool disease (fungus)

SignsWhite cotton-like growth on wounds or snout, loss of appetite, staying motionless

PreventionPrevent abrasions. No rough substrate or sharp driftwood. Keep water at 20°C or above

Paracolo disease (Edwardsiella)

SignsRedness and swelling around the vent, swollen belly, bleeding at fin bases, sudden loss of appetite

PreventionAvoid overcrowding and poor water quality in hot periods. Remove leftover food every time; change 1/3 of the water weekly

Red spot disease

SignsSpreading red pinpoint bleeding on belly and lower jaw, lying still on the bottom, not eating

PreventionCommon in cold periods (below 20°C). Keep temperature stable with a heater; avoid abrupt water changes

Gill disease

SignsGill covers stuck open, rapid breathing, gathering near the surface or in strong current

PreventionKeep ammonia and nitrite at zero. Clean the filter and keep stocking density appropriate

Swim bladder nematode (Anguillicola)

SignsFloats at the surface and cannot sink, swollen belly, thin body with only the belly enlarged

PreventionDo not feed wild-caught live food. Have wild-origin eels examined and fecal-tested before bringing them home

Jumping out, drying out

PreventionWeighted lid; cover pipe and cable holes with fine mesh. Keep the water level 5 cm or more below the rim

First aidReturn to the tank with wet hands and set aeration to maximum. Rinse off sand and debris with tank water. Eels breathe through their skin, so do not give up

Abrasions, torn mouth

PreventionDo not chase with a net. Move by scooping up with water in a container. No sharp decor

First aidObserve the wound without removing from water. Keep water quality optimal; if cotton-like growth appears, treat as fungus and consult the same day

Stuck in a gap

PreventionPipe and driftwood openings should be at least twice the body diameter. Cover narrow pipe ends with mesh

First aidDo not pull. Lift out the whole fixture underwater and free the eel gently. If the body stays bent, see a vet immediately

Falls, blunt trauma

PreventionWork close to the floor when the eel is out of the tank. Use a lidded bucket and carry it with both arms

First aidCheck for bleeding or a bent body and return to the tank. Persistent tilting or spinning suggests spinal injury; see a vet immediately

Edwardsiellosis

RouteThrough cuts on hands that touch tank water or the fish. Accidentally swallowing tank water

PreventionWear gloves if you have cuts. Wash with soap after work; never get tank water in your mouth

Vibrio wound infection

RouteContact of wounds with brackish or marine tank water or the fish

PreventionPeople with liver disease or diabetes must wear gloves. If a wound suddenly swells with fever, go to the ER immediately

Fish tank granuloma

RouteMycobacteria enter through hand cuts sustained while cleaning the tank

PreventionClean with long gloves. Tell a dermatologist about fish contact if hand swelling or nodules will not heal

Aeromonas infection

RouteContact of wounds with tank water or the fish, swallowing tank water

PreventionWash hands after work. Children and the elderly must wash thoroughly; do not handle tank water in the kitchen sink

Food

• Eel formula feed (paste) or sinking carnivore pellets
• Supplement with frozen bloodworms, chopped fish or shrimp 2–3 times a week
• Feed once nightly, as much as is eaten in 5 minutes. Reduce below 22°C

Water

• Dechlorinated fresh water. pH 6.5–7.5, zero ammonia and nitrite
• Change 1/3 weekly. Keep temperature difference within 2°C and add slowly by drip

Toys & play

• Several PVC pipes or clay pipes the eel can fit into completely
• Tame it by offering food by hand or tweezers at night feeding
• Create a gentle current and leave space to swim around

Nest, bed & hideout

• Fix a PVC pipe with inner diameter at least twice the body to the bottom
• Keep lighting dim and point the pipe entrance toward the back of the tank

Bedding & litter

• Fine, rounded sand or no substrate at all (bare tank)
• Avoid sharp gravel and pointed driftwood that damage the skin
• Siphon out waste and leftover food daily to keep the bottom clean

Cage / housing material

Glass or acrylic tank. A weighted, gap-free lid is essential

Size & space

60 cm tank for juveniles; 90–120 cm tank (150 L or more) for adults

Layout

• Place several hide pipes; cover the openings of a hang-on filter with mesh
• Keep the water level 5 cm or more below the rim; fit a heater guard
• Seal pipe and cable holes completely with sponge or mesh

Placement notes

• Avoid direct sunlight, vibration and high-traffic areas
• Check floor load capacity, set on a level stand and prepare for leaks

Exercise, free-roam & walks

• No walks needed. Provide room to swim around at night
• Do not take it out of the tank. Move it in a container with water
• When working with the lid open, do not look away and finish quickly

Temperature & humidity

Temperature22–28°C. Appetite drops below 20°C; above 30°C is dangerous

HumidityNot needed; it lives in water. Watch for lid condensation and leaks indoors

Summer & winter

• In summer, use a cooling fan or chiller to stay under 28°C. Watch for oxygen depletion
• In winter, keep 22°C or above with a heater, or manage dormancy at around 15°C

Nail trimming

No claws. Instead, check the mucus coat weekly for wounds, white spots or bleeding

Brushing, skin & coat care

No brushing. The mucus is a protective layer, so do not touch with bare hands. Rinse off debris with tank water

Other care

Rinse the filter and hide pipes in tank water once a month. Test and log water quality weekly with a thermometer and test kit

Protection from predators

• Weight the lid and choose a location so cats and birds cannot climb on it
• Outdoor ponds and tanks are targeted by herons and raccoons
• Avoid tank mates that are large predators or small fish that fit in its mouth

Foreign-body ingestion

May swallow substrate or pebbles with food. Do not use large gravel or leave anything it cannot spit out. See a vet for a bloated belly or no feces

Being stepped on

Stepping on an escaped eel on the floor breaks its spine. If one is on the floor, turn on the lights, watch your feet and pick it up gently with wet hands

Getting pinched

The body gets caught in lid gaps or pipes and the skin tears. Check its position before closing the lid. If stuck, free it underwater with the fixture

Falls

Can leap 1 m out of the tank onto the floor. After a fall, check for bleeding or a bent body and return to the tank. Persistent tilting or spinning: see a vet immediately

Escape

Gets out through a 1 cm gap. Weight the lid, cover holes with mesh. If it escapes, search dark corners, under furniture and drains; wrap in a wet towel and return it

Safe release procedure

1. Keep the bitten hand in the water and wait for the eel to let go on its own
2. If it does not release, press lightly behind the gill cover and the mouth will open
3. Once free, return the eel to the tank, do not chase it, and turn off the lights to let it rest
4. Rinse your hand well under running water; keep slime and blood out of your eyes and mouth

After the release

Wash the wound with soap and running water and disinfect. Swelling, heat or red streaks suggest bacterial infection; see a doctor the same day

What to tell the vet & what to bring

Temperature, pH, ammonia and nitrite readings, last water-change date, photos of symptoms, tank size and tank mates. Transport the fish in its own tank water

Checking consciousness, breathing & heartbeat

• Check breathing by gill-cover movement: 40–80 per minute at rest
• Touch lightly to see if it flees. No response or lying on its side is critical
• If the skin is still moist, it may survive by skin breathing

Stopping bleeding

• Keep the fish in water and observe there. Do not use styptics or antiseptics
• Do not touch the bleeding site; keep water quality optimal to prevent secondary infection
• Eel blood causes inflammation if it gets into eyes or cuts. Wear gloves and wash hands thoroughly

Transport

• Double-bag in heavy bags with 1/3 tank water and air; carry in a dark box
• Tie the bags tightly. Keep water at 22–26°C, avoid shaking and keep the trip short