Why Did My Pet Fish Die? 6 Common Reasons

There are a lot of new things to learn when setting up a community aquarium at home. Every fish species has different needs and behavioral patterns that need to be taken into account. The thing is that all of us make mistakes while learning and it is completely normal.

At the beginning, you might feel like you did everything right and your fish seem pretty happy too. Then, one day you find a dead fish floating in the water. What happened? You really can’t put the whole picture together in your head at the moment and this can be frustrating.

Don’t worry this happens to all of us. What you need to focus on instead is to identify your mistakes and make sure they won’t happen again.

Reasons Why Pet Fish Die

A home aquarium is a complex system and your fish need it to be in a certain state in order to feel safe and healthy. Water temperature, pH, filtration, ammonia and nitrite levels, tank size and fish temperament all play a huge role, just to mention a few.

There are plenty of hardy fish to choose from in the aquarium trade but still, it is enough to do one thing wrong and diseases might emerge. Below, I am going to bring your attention to the most important factors that can play a role in making your fish sick.

– Poor Water Quality

You really can’t afford not to filter or change the water because water quality is a huge factor when it comes to fish health. When the water parameters are bad or the water is dirty, it always causes a chemical imbalance.

Being exposed to poor water quality for a long period of time is extremely unhealthy for your fish. First they get sick, and then they eventually die. One way to counter this is to get a testing kit and make sure the water parameters are ideal.

If they are not, you need to fix the issue as soon as possible. You need to measure pH, nitrates, ammonia and nitrite as well. The ideal pH level really depends on the fish species you keep in the aquarium so you need to do the research on that.

– The Aquarium is Not Established

When you buy your fish, you need to put them into an aquarium that is well-established. This means that proper cycling has been done and beneficial bacteria are present in the water. Clean tap water is simply not enough for aquarium fish because that’s not what they have out in nature.

The thing is that those bacteria need time to develop in your filter and the substrate. The reason why they are so beneficial is that they help dealing with waste and also contribute to the overall health of your fish. There are various ways to cycle your new tank before putting in the fish.

You can research those and choose the method you like the most. Adding too many fishes in the tank at once is another common issue.

– Overfeeding

There are many different fish species you can keep at home and their diet can differ to a significant degree. However, you can’t go wrong by feeding all of them once per day. Just make sure that they are eating as much as they want to and then collect the leftover food.

This way, you can make sure they won’t be overfed. The problem with overfeeding is that the ammonia level in the tank is instantly going to rise. It is not only unhealthy for your fish but they will also produce a lot more waste. Not to mention the leftover food that accumulates in the aquarium day by day and contaminates the water as it decomposes.

Overfeeding leads to waste and leftover food which leads to rapid algae growth. A nice solution to this problem is to get an algae eater fish or two.

– Overcrowded Tank

You can either choose the fish you want to keep based on the aquarium you have bought or the other way around. Either way, the aquarium has to be big enough for your fish to thrive. In case it is small, there will be a buildup of contaminants in the water and your fish are going to get sick.

Another problem with overcrowding is that your fish are not going to have enough private space. This can cause conflicts between them. Even if they won’t bully each other, they are going to be extremely stressed because of the lack of space.

– Aggressive Tank Mates

Making sure that your fish are compatible is one of the first things to consider when setting up the aquarium. If you pick an aggressive and territorial fish and don’t match it with the right species, it can end up chasing, bullying and sometimes even killing its tank mates.

If you want to keep aggressive fish, make sure that the size of their tank mates is similar or bigger. Other fish in the tank should also be able to defend themselves. In case your fish are territorial, then make sure there is enough space for them so that they can claim their territory.

Choosing the right tank mates is really about knowing what each of your fish need and understanding their personality. This is why I often recommend doing some research about each and every fish you are about to buy. If you notice any aggression in your already established tank, then make sure to remove the aggressor as soon as possible.

– Disease or Parasites

One day you might notice that your fish is doing something weird or that its appearance has changed. Maybe there is a lesion, a bulge on its body or it seems like your fish is just lethargic and unwilling to eat. Now, I’m not saying that your fish doing something unexpected necessarily means that it is sick.

However, if you are not sure what is happening, then you should definitely start thinking and try to verify whether your fish is sick or not. There are quite a lot of diseases and parasites that can emerge in a home aquarium. The two most typical causes are dirty water and stress.

Regular water changes, proper filtration, regular cleaning and keeping the tank stress-free are very important things to focus on. If you do them right, then it is going to be very unlikely that your fish get sick.

The first step when you notice that something is wrong is to try to identify the symptoms and do some research on the internet. For questions and treatment advice, you can always call your local veterinarian or fish keeping expert.

Wrap Up

Finding out that your fish is no longer alive is definitely an eye-opening experience. However, I’m here to tell you that this can happen to every beginner fish keeper. What is most important is to learn from your mistakes and you are eventually going to become an experienced fish keeper.

Hopefully, my article about the main causes of fish dying has helped you figure out how to do things better as a fish enthusiast. If you have just started out, I recommend that you keep some beginner-friendly fish until keeping them healthy and thriving becomes effortless for you.

Fishkeeping   Updated: September 27, 2021
avatar Hey, I'm Fabian, chief editor at Aquarium Nexus. I really enjoy the aquarium hobby and love sharing my experience with others. If you have any questions feel free to contact me or leave a comment below.

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