Why do Pond Fish Die?

There are many reasons why pond fish die, water quality, suffocation, pesticides, disease, starvation, stress, predators, old age and more.

In this article we will go through the main possibilities of why, plus a few other facts you might be intersted in.

Water Quality

The first thing to look at is water quality, it’s a big factor when it comes to your fishes health, just because your pond looks nice and clear does’nt mean that the water is good for your fish.

Oxygen: or should I say lack of oxygen, if there is not enough oxygen in your pond your fish will suffocate, your fish need oxygen to breath, if you see your fish on the surface gasping for breath this could be caused by lack of oxygen.

Ammonia: another thing to consider is ammonia in your pond, this is caused by waste (poo) from your fish, uneaten food and rotting debris like leaves that fall into your pond. Ammonia gets into your fishes gills which affects your how you fish breathes, when this happens you will more than likely see your fish on their side at the surface of the water gasping for breath.

Pesticides: it seems odd that I would add pesticides to water quality but it is possible for pesticides to get into your pond water, usually from products that you use in your garden, when spraying its possible that the pesticides get blown into your pond.


Fish will die of starvation, if they don’t eat they die, the reasons why they starve could be because they are not fed due to the owner going on holiday or a weaker fish that doesn’t get any food when the fish are feed.

Fish will normally live for a couple of weeks without being fed, but any more than that could be fatal.


Just like us, fish get stressed and if a fish gets stressed it can lead to sick fish, it can weaken their immune system which makes them more prone to attacks from pathogens, parasites and bacteria, if left untreated your fish could die.


Viral, parasitic and bacterial disease is a big killer of pond fish, you can’t see it with a naked eye but if you notice a lot of fish acting strangely, not feeding, spread or clamped fins, lethargic or just hanging in the water it’s more likely you have an outbreak in your pond that will need to be treated as soon as possible.


Herons are probably pond fishes biggest predator, but cats dogs, otters and others can attack your pond, if your fish are missing its probably been taken, but sometimes your fish are just injured in the attack, but die latter.


Not the ones you wear, this is when a fish jumps out of your pond and lands on the ground around it, if you ever see fish lying dead outside your pond this could explain it.

Old Age

It comes to all of us, and when the time comes we will die of old age, it’s the same for fish.

Other reasons pond fish die

Spawning: it’s a sad fact that during reproduction fish can die, it is just too much for them to take.

Cold Weather: during the coldest time of the year it’s not unusual to loose a fish or two.

Heat: extreme heat can raise you fishes metabolism which could shorten their lifespan.

Food: a poor diet, if fish are feed a poor quality fish food they might not get the nutritional requirements they need, overfeeding could also shorten the life of a fish.

What do you do if a pond fish dies

You should check to see why the fish has died, if you suspect it’s from a disease you should treat the whole pond, test the water quality to see if there is an underlying problem and treat accordingly, also check for signs of deoxygenating.

Should you remove dead fish from a pond

If you find a dead fish floating in your pond you should remove it straight away, if you leave it in your pond it would decompose polluting the water and putting the remaining fish at risk.

If you leave the dead fish in your pond other fish might eat it and if the dead fish died of a disease it could pass it on to your healthy fish.

Is it illegal to flush a dead fish down the toilet

The law states that non-native fish should not be disposed of by flushing down a toilet, especially if they have died through disease. Dead fish are best cremated, but you could bury them or tie them up in a bin bag and put it out with your rubbish.

Do other fish get sad if a fish dies

Although it would be nice if other fish felt a bit sad if another fish dies, they don’t, a fishes brain is not capable of showing that type of emotion, in fact they are more likely to eat their former friend.

Can you revive a dead fish

If you catch a fish quickly enough there is a slim chance you can revive it, but if it’s been dead for a while you will have to let it go.

Should you kill a dying pond fish

It’s a sad time when you see one of your fish dying, but sometimes it’s in the best interest of your fish that you euthanise it to stop it suffering.

Do fish know they are dying

It’s more than likely fish don’t know they are dying, they might feel pain or stress, but they don’t know they are dying.

Does salt help a dying fish

If your fish has a disease or parasites you can give your fish a salt bath to help, you need to quarantine the fish in a bucket of pond water with the right amount of salt, hopefully this will stop your fish from dying.

How do you know if an old fish is dying

If your old fish is eating less and getting slower this could be a sign that it’s dying, if it looks less healthy and is discoloured these are more symptoms that it’s getting old and about to pass.

Other symptoms include loss of weight, bulging eyes, floating on their side and trouble breathing.

How do fish act when they are dying

Telltale signs that a fish is dying are not eating, trouble breathing or gasping for air at the waters surface, discoloured gills, bloating, swimming funny (upside down), bulging eyes, isolation from other fish and physical injury. 

Why do fish float when they die

When a fish dies they don’t always float to the surface straight away, sometimes they sink to the bottom of your pond, but as they start to decompose gases are released into their body, they already have the remains of the oxygen from when they were alive and the two of these fills the belly of the fish which makes it float to the surface, so it’s the oxygen and gasses that makes a dead fish float.