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Can Fish Have Heart Attacks?

If you have ever lost a fish suddenly and it has swum around violently before abruptly stopping, you may have wondered, “can fish have heart attacks?”.

It’s difficult to say, but since fish do have hearts, it’s likely that they can suffer from some form of heart attack, just like many other animals can – even if it seems like an odd idea.

Fish may sometimes have a heart attack if something shocks them or something goes wrong with their systems.

Few fish will have heart attacks, and you might keep fish for a long time without ever seeing one have a heart attack.

However, if you have had a fish die suddenly with little visible cause, it is possible that it has had a heart attack, although you will probably never know for sure. If this does occur, it’s a good idea to keep the fish in a separate tank for a short while to check that it is actually dead, and not stunned.

If something has happened to one of your fish, you should check on all other inhabitants of the tank to make sure that they are okay and nothing is affecting the water.

Sudden death could also be caused by a toxin in the water or some unseen infection, so don’t immediately assume it was a heart attack. Fish are quite delicate creatures and can be killed by all sorts of things, with the cause often being hard to detect.

Can Fish Have Heart Attacks?

It is thought that fish can have heart attacks, yes, although there is little evidence to support this besides the fact that fish have hearts and circulatory systems that are not dissimilar to those of animals that certainly can have heart attacks.

It is logical that a fish may be able to suffer from a kind of heart attack, because if something goes wrong with its circulation, blood will stop getting to the heart, and this is a form of heart attack.

However, fish probably won’t suffer from a heart attack in the way that a person would, because they don’t have to deal with high cholesterol or other risks associated with heart disease.

If your fish has died suddenly, you should investigate the potential causes, and not automatically assume it was a heart attack. You may find that something else killed the fish, which could have an impact upon its tank mates, and therefore will need addressing.

So far, little scientific research has been done into fish heart attacks, what causes them, and whether they even suffer from them in the same way that humans do.

In the future, we may have a greater understanding of how this works and how likely fish are to have heart attacks. Often, what appears to be a heart attack will be accompanied by a few violent flips or frantic swimming for a few seconds before the fish ceases moving.

Can Fish Have Strokes?

It isn’t really known whether fish can have strokes either, but as with heart attacks, it seems reasonable to assume that they could.

A stroke is caused by blood clotting somewhere that it isn’t supposed to clot, so in theory at least, a fish could suffer from a stroke. However, you are unlikely to ever be able to tell whether a fish has had a stroke.

Sometimes, fish seem to only be moving body parts on one half of the body, and may swim in circles, which might make you feel like a fish has had a stroke – and it may have done so. However, there could be other explanations, including a bacterial infection affecting the fish’s motor skills.

If you are concerned about a fish that is swimming oddly, you may wish to quarantine it from your other fish and treat it with some antibiotics to see if this clears up the issue.

It won’t if the fish has had a stroke, but it may help if the issue is caused by something else, so it’s worth trying if you’re stuck.

If you can take your fish to a vet, they may be able to check whether the fish has had a stroke, but it is unlikely to give you a conclusive answer. It’s a good idea to check for any contagious causes so that you know whether you need to treat your other fish.

Can You Reduce The Chances Of Your Fish Having A Heart Attack Or Stroke?

A fish is probably at most risk of a heart attack if something shocks it, so it’s a good idea to minimize stress as much as you can.

When you introduce a fish to a new tank, make sure you do so slowly to avoid temperature stress and the shock of new water. You should also ensure that the tank is suitable, with the correct amount of compatible fish.

Tanks should have plenty of places for the fish to hide in, a good filtration system, and water conditioners if necessary to reduce fish stress.

When adding a fish, submerge it in its bag for a while to allow it to get used to the situation before shocking it with the water change and freedom of the tank. If you see any signs of bullying in the tank, you should remove the offending fish and isolate it or put it into a different tank with other fish.

Do not place a fish in a tank that is overcrowded, dirty, heavy in ammonia, or with unstable temperatures. Although this doesn’t guarantee that the fish will not have a heart attack or a stroke, it may help to reduce its risk.


So, the answer to the question “can fish have heart attacks?” is that nobody really knows for sure yet, but it is quite likely that it can happen in certain situations. Fish have hearts that are similar to those of other animals, and there is no reason to believe that they cannot have a heart attack if the blood stops flowing properly. The same applies to a fish having a stroke; if the blood clots somewhere in the fish’s body, it could cause one.