How to dispose of dead fish, and what to do when you find one

If you find a dead fish in your tank, take it out straight away, then test the water for ammonia and check your other fish. To dispose of it, wrap it and put it in the household bin, or bury it deep in the garden. Don't flush it: fish diseases can reach rivers and lakes, and dead fish can block pipes.

Losing a fish is upsetting, especially if you don't know why. A few quick checks now can tell you whether it was a one-off or a warning sign for the rest of the tank.

What you need

A fish net, or a small cup or bag to lift the body out
Gloves, especially if you have cuts on your hands (see fish TB)
A water test kit for ammonia, nitrite, nitrate and pH
A thermometer
Paper towel and a sealable plastic bag
A phone to take photos

Step by step

1. Make sure it is really dead

Some fish play dead, rest in odd positions, or lie still when stressed. Plecos, loaches and some catfish often wedge themselves in strange places. Look for gill movement for a minute, and give it a gentle nudge with the net. A dead fish has no gill movement, does not react, and its eyes often turn cloudy.

If the fish is still alive but clearly dying and suffering, see our dropsy guide for humane euthanasia. Never flush or freeze a living fish.

2. Remove it right away

In warm tropical water a body starts to rot within hours. That releases ammonia, which can poison the other fish. Tankmates may also eat the body, and that is how several diseases spread, including neon tetra disease, fish TB and worms.

If you can't see a fish you know is in the tank, look in caves, behind the filter, under decor and inside the filter intake. A missing fish may have jumped out, so check the floor behind the tank too.

3. Test the water

Test ammonia, nitrite, nitrate and pH, and check the temperature. If ammonia or nitrite is above zero, do a 30–50% water change with dechlorinated, temperature-matched water. See ammonia and nitrite. Also check that the heater, filter and air pump are working.

4. Look at the body for clues

Lay the fish on a paper towel and take photos in good light. Look for:

White spots: ich
Fuzzy or cottony patches: fungus or columnaris
Ragged, rotting fins: fin rot
Scales sticking out like a pine cone, or a swollen belly: dropsy or bloating
Bulging eyes: popeye
Very thin body: worms, poor feeding, or a chronic disease
Red threads at the vent: Camallanus
Torn fins or missing scales: aggression
Red streaks, red gills or no clear sign at all: often a water problem such as ammonia, nitrite, chlorine, or temperature

A fish with no marks at all may have died of old age. See fish lifespan.

5. Check the other fish

Watch the tank for 10 minutes. Are any fish gasping, flashing, hiding, clamping their fins, or off their food? If several fish look unwell, see fish dying one by one and act today.

6. Decide whether to keep the body for a vet

Keep the body if several fish have died, if more look sick, or if the fish was valuable. A lab can sometimes find the cause, but timing matters:

A fish dead for more than a few hours, or one that is soft, smelly or has cloudy eyes and pale gills, is usually too far gone to test.
A freshly dead fish with clear eyes and red gills is more useful.
Wrap it in damp paper towel, seal it in a plastic bag, and keep it in the fridge, not the freezer. Freezing damages the tissues a lab needs to see.
Call a vet or fish diagnostic lab before you take it in. They often prefer a live, sick fish from the same tank over a dead one.
Also collect a water sample in a clean jar before your water change.

7. Dispose of it

Household bin: wrap the fish in paper, seal it in a bag, and put it in the outside bin. This is the simplest choice and suits most fish.
Burial: bury it in the garden, deep enough that dogs, cats, foxes or raccoons can't dig it up, and away from ponds, streams and vegetable beds.
Your vet: some vets offer cremation for pets, including large fish.
Not the toilet. Flushed fish can carry diseases and parasites into local waterways, where they can harm wild fish. Sewage systems don't always remove them, and some pipes lead straight to rivers. Larger fish can also block plumbing.
Not a pond, river or lake. Never put a dead or live aquarium fish, plants or tank water into the wild. In many places it is illegal.

Wash your hands well afterwards, and wash the net in hot water.

A gentle note on kids and grief

For many children, a fish is their first pet and their first loss. Be honest and simple: "Our fish died. Its body stopped working and it can't come back." Avoid saying it "went to sleep", which can make bedtime scary. Let your child help with a small burial or a drawing if they want to. Feeling sad is normal for adults too. Avoid rushing out to replace the fish the same day. Find out what happened first, so the next fish has the best chance.

Common mistakes

Leaving the body in "to see what happens". It pollutes the water and spreads disease.
Flushing it.
Not testing the water. Many deaths are water problems that will affect the other fish next.
Adding medicine straight away without knowing the cause.
Freezing a body you want tested.
Replacing the fish immediately without quarantine. See our quarantine guide.

Products that help

Liquid water test kit: the most important tool after any death.
Dechlorinator: for an emergency water change.
Disposable gloves: protect your hands from infection.
Spare net: kept just for sick or dead fish.
Tank lid: prevents deaths from jumping.

How to prevent it

Count your fish every day at feeding time, so you notice a missing fish fast.
Test water every week or two.
Quarantine new fish for 4–6 weeks.
Don't overstock or overfeed. See overfeeding.
Keep a lid on the tank.

Why it happened

The most common causes are water problems (ammonia, nitrite, chlorine, or temperature), disease brought in by new fish, bullying, jumping, and old age. A single death in an old fish with clean water is often natural. Several deaths close together usually point to the water or an infection.

When to get help

Contact an aquatic vet or experienced fish shop if more than one fish dies in a week, if others look sick, or if the water tests fine and you can't see why. Bring photos, your test results and, if possible, a freshly chilled body or a live sick fish.

In the game

Multiple Tank Syndrome doesn't have a "dead fish" card yet.