Why Did My Cardinal Fish Died? 6 reasons explained

Why did my Cardinal fish die?

Cardinal Tetra popularly known as Cardinal fish is a beginner-friendly fish that could be kept and taken care of by anyone, including those with zero fish keeping knowledge because they are hardy and are not very expensive to keep. Despite that, it does not mean that they are invincible to death or problems. If you are reading this article, it means you want to know why your Cardinal fish died or why they are dying. In this article, you will learn all about that and many more.

Why did my Cardinal fish die? Cardinal fish could die as a result of the presence of toxins in their water, Diseases, or parasites.

There are many factors that could lead to the death of fish of any type, be it the hardy or the fragile fish.

You will agree with me that losing such fine fish like Cardinal fish could be very sad and heartbreaking, so what are the factors that could lead to their death and the possible ways to prevent them from dying.

Why Cardinal Fish Might Die

1. Lack of feeding: Although fish of all types will last for days and even a few weeks without food before they could go down but they will die in the long run.

Asking why your fish died, we all know that some of us do travel without anybody at home or office that could take care of our fish, at least to be feeding them.

No living thing can survive for long without food and fish are no exemption from this.

According to a survey, almost 10% of the mortality rate in fish is caused by hunger or toxic foods.

For those that travel, I have something for you, buy an Automatic Feeder and place it on your fish tank with foods like pellets loaded and it will be feeding them automatically until you come back.

Sounds cool right?.

Again try to buy quality foods for your fish and mix their diets with manufactured foods like pellets and meat like brine shrimps, etc.

2. Toxins: Toxins such as ammonia, copper, nitrites, chlorine, etc are very dangerous for any aquatic animal, including fish of any type.

These come into tanks through many means such as dirt, water sources, etc and they could kill any fish if nothing is done about it.

As an Aquarist, you must have water testing kits so that you could be able to test your aquarium water every week so that you could be able to keep an eye on these deadly toxins.

So buy water testing kits and keep them.

Try as much as possible to do a 50% change of water once you notice any of these toxins.

Also, you must have a Filter to help you keep the water filtered and clean always.

3. Wrong water parameters: Every aquatic animal has its ideal type of water and water requirements and when these are not in place could cause them some health issues which could easily lead to death.

The ideal water parameters for Cardinal fish is

Temperature – 68°F – 82°F.

pH – 8.0 – 8.5.

When these are not set right, especially the temperature, the fish could suffer from some health issues and might die.

Cardinals are tropical fish and so will need a heater to maintain a steady temperature as I mentioned above. So get one for them.

4. Unsuitable Tank Mates: Cardinal Tetras are semi-aggressive fish and sometimes they could even fight and kill each other.

Although some species are not aggressive and territorial, some are, like the Banggai Cardinal fish, etc.

Again, they could be easily stressed, and keeping aggressive fish or any aggressive animal is not advisable as they could be stressed to death or even be eaten.

Your Cardinal fish could be dying as a result of aggression, so check their tank mates and remove the aggressive ones.

Also, it is not advisable to keep more than two of the aggressive species in one tank because once the first two pairs, they will join force and take down the third.

So, even if you want to keep more than two of the Aggressive species, make sure that your tank is about 120 gallons or more so that they will have enough space and avoid each other a bit.

5. Diseases and parasites: Despite that, some fish are resistant to some diseases and parasites, and no fish is completely immune to them.

There are many diseases and parasites that could infect Cardinal fish which could lead to death if nothing is done about it.

Diseases and parasites like white spot or Ich, fin rot, swim bladder bloat, etc could infect and cause death if not treated on time.

As we always say, we don’t give medical advice, so get a vet doctor if your fish is sick.

6. Old age: Another reason why your Cardinal fish died could be because it has exceeded its lifespan.

Every living thing has a specific lifespan and when it exceeds it, it will die.

The lifespan of Cardinal fish is between 5 – 7 years, depending on how they are taken care of.

So, if you think your fish just died and you seem to find nothing wrong, then I think you might have to calculate the age of your fish, it could help you to maybe conclude if it died of old age or some other factors.

How Do You Know When A Tetra Fish Is Dying?

You must not wait for your fish to die before you do something, maybe to save them, so the question is, how do you know that your fish is about to die. Some of the signs are:

Fin rot.



Swimming Upside-Down.

Lose of coloration.

Dullness, etc.

These are some of the signs to notice when something is wrong with your Tetra fish and what you must do is tackle the problem adequately and save your fish from dying


These are some of the factors that could lead to the death of your Cardinal fish.

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