Why Do My Aquarium Fish Keep Dying?

By Josie F. Turner, Journalist specialized in Animal Welfare. May 9, 2021
Why Do My Aquarium Fish Keep Dying?

Being a lover of pet fish has many rewards. Not only are they beautiful to look at, but they have calming and stress-releasing effects on humans. Unfortunately, many fish species do not have very long life cycles. This means one of the disadvantages is that many will die under our care. However, a fish reaching the end of their natural life cycle is not the only way they can die. Too many fish die to a lack of proper care. Often it is not active neglect which leads to this, but misunderstanding of their care needs.

At AnimalWised, we answer the question why do my aquarium fish keep dying? We present the most common reasons why pet fish die and help you to understand what you can do to prevent this from happening.

You may also be interested in: Why Are My Fish Not Eating?

Stress and illness

Fish are very sensitive animals. Not only are they susceptible to disease, but their sensitivity to stress is one of the most important factors in fish death. Often disease can lead to stress and vice versa, so protecting them from both is one of the most important ways of safeguarding their well-being.

Diseases in aquarium fish

As soon as you take your pet fish home from the pet store, we need to be very attentive to the common symptoms of disease in fish. Even though the store owners might do their best to protect fish from disease, there are multiple fish kept in various aquaria. This means disease can spread relatively easily.

Although it is difficult to detect disease in fish, the most common symptoms of disease in fish include:

If you see the fish you want to buy is displaying any of these characteristics, we recommend you don't get them. Nor should you purchase any other fish from the same tank. Although the other fish may not be displaying any obvious symptoms, they are likely to become infected if they share the same water with them.

Stress in aquarium fish

Another important reason why your fish keep dying is due to stress. All companion animals will be affected by stress, but few are as sensitive as aquarium fish. This is something we need to consider from the very beginning. When you purchase your fish, taking them home can be a stressful occasion. If we knock the bag, shake it or even leaving them in the sun can cause them to become stressed.

Another common reason why fish keep dying due to stress is having too many share the same space. When a fish tank is overcrowded, it will not only seriously affect the aquarium's hygiene, but it will mean they keep knocking into each other. They will become stressed over their access to resources such as food. When the fish become stressed they can also become aggressive. This means they can attack and even kill other fish.

Even when your aquarium is large enough for the number of fish you have, they can become stressed when you need to change the water. During this process, you will need to temporarily relocate the fish or significantly reduce the amount of water in the tank. This means the fish are in very close company and the entire process can be stressful. Minimize this process as much as possible or separate them into different buckets.

Another common reason for stress in fish is to do with our behavior. Fish are not used to human interaction. Our touch can be very distressing for them. Do not pick the animal up with your hands since the pressure we put on them can make them feel as if they are under attack. Use a net or a small bowl to catch the fish.

Although we may have good intentions, tapping the glass must be avoided. This is something children often do without thinking, so we need to ensure they know how to treat the aquarium.

Avoid stress in fish

Although precious, our fish will be very delicate. At all costs, you will need to avoid episodes of stress. This will mean they are less likely to develop other diseases, avoid a premature death and best guarantee their well-being.

If you have visited a public aquarium, you will likely have seen notices which say ‘do not tap the glass’ or ‘no flash photography’. We recommend using the same restrictions for your home aquarium. Ensure you don't cause them any unnecessary stress with your behavior.

Ensure you know how much water you need for your aquarium given the amount and species of fish you have. Meet your responsibility as a care giver and ensure all their basic needs are met. Feed them the right amount of food and do so while adhering to a good routine.

Why Do My Aquarium Fish Keep Dying? -

The impoirtance of water

Water quality is also one of the most important factors as to why your fish keep dying. Since water is essential for their their survival, it makes sense that poor water quality will negatively impact their health. Incorrect water temperature, poor cleaning and other water issues can be fatal to our fish. Below we look into these issues more closely.

Control of ammonia and oxygen

There are two very important factors which affect an aquarium's water quality. These are the levels of both oxygen and ammonia. Oxygen is essential for a fish to survive as they will not be able to respire without it. Nitrogen is emitted by the fish via their waste. When the aquarium has too little oxygen or too much ammonia, it can kill them.

How much oxygen and ammonia is dependent on the type and species of fish. Not all fish can tolerate the same level of oxygen. For example, catfish are considered ‘bottom feeders’ and are used to having less oxygen than fish which live closer to sea level. These fish are also known as clean-up animals since they eat a lot of the debris left by other fish.

You will need to check the oxygen and ammonia levels periodically. To do this you will need special testing kits, which can be expensive. If you take care of your aquarium, have all the right elements and maintain it carefully, there should be no reason there isn't enough oxygen in the tank. If the fish are gasping for air, we see any of the above symptoms mentioned, you should check the oxygen and ammonia levels.

Temperature and salinity

Temperature is also very important to sustain your fish's life. Generally, pet fish are divided into two categories: tropical and cold water fish (also known as freshwater fish). As their names suggest, tropical fish will require warmer temperatures than cold water fish. This will require careful monitoring the temperatures and you will not be able to keep one fish type with the other in the same tank.

Tropical fish will also need higher salinity than freshwater fish. As an average guide, tropical fish will need a salinity of about 35 PPT (35 parts salt to every 1000 parts water). However, there are different factors which will affect these levels, including temperature, types of plant and changing the water. A hydrometer can be used to check the salinity, but it is not as precise as an electronic salinity monitor.

Take a look at our article on the best freshwater fish for a cold water aquarium to know more.

Excrement and hygiene

As stated above, a fish's excrement can affect the ammonia levels in the aquarium. If the water is not properly filtered and the tank cleaned regularly, then the fish waste can build up. Some aquarium plants can be used to convert the ammonia and prevent harming the fish, but this will also require some research as not all plants are good for all fish.

Decomposition of food and eve the death of any living beings in the tank can affect ammonia levels. We need to ensure we don't overfeed the fish and clean it regularly to remove any debris. To keep the water clean, it should be enough to do partial water changes on a regular basis and ensure you have a good filtration system.

Overcleaning the aquarium

Maintaining the water in an aquarium is not as simple as it seems. In addition to the help provided by a quality filter, the water in an aquarium needs to be renewed from time to time and if we remember that fish are very sensitive animals, this process can be traumatic for them.

When renewing the water in an aquarium, in addition to taking into account what we mentioned about not gathering too many fish in confined spaces, you must conserve at least 40% of that ‘old’ water before adding new water. Otherwise, the fish would not adapt to the change and would die. This old water must have been treated to eliminate as much ammonia as possible to be able to mix with the new one and thus renew the liquid environment of your aquarium.

On the other hand, the new water for the aquarium should never be tap water. Chlorine and lime concentrated in the water, which for humans is harmless, could kill your fish. Always use sterile water and if possible, make sure it does not contain any type of additives.

Another important aspect is to use excessively clean materials. Make sure that the buckets where you will pour the water or the fish themselves have a little of that old water or at least check that they have absolutely no traces of soap or cleaning products. In any case, do not forget that you can never use the same products with which you clean your house to clean your aquarium or the material that is in contact with the fish.

Why Do My Aquarium Fish Keep Dying? -

Tips to prevent fish from dying

Despite mastering the arts of caring for fish, some may occasionally die or become ill without warning. Unfortunately, this can happen, even if there doesn't seem to be any obvious cause. As with all illness, prevention is the best treatment.

The most important thing is that you keep in mind the aspects that we have already mentioned and, of course, always use common sense. If you know that fish are sensitive and delicate animals but you treat them roughly, you should look inward for the answer as to why your fish keep dying.

To best keep your fish alive and well, here are some general guidelines to follow:

  • Handle them gently and delicately when changing the water in the fish tank.
  • If you acquire new fish, introduce them to safely in to the aquarium.
  • Always ensure your fish are compatible with each other. For example, betta fish can be very aggressive and will not be able to live with many other fish species.
  • If you have visitors or small children at home, ensure they know how to treat the aquarium properly.
  • Do not overdo the amount of food that increases the level of ammonia and the appearance of bacteria in the water.
  • Check the recommended water, temperature, light level and oxygen level specifications for the types of fish you want to have. Test the water regularly.
  • If you are going to decorate your aquarium, buy quality plants and other accessories. Verify that they are suitable for aquariums and do not contain pollutants.
  • Have a large enough aquarium for the type of fish you have and don't overcrowd the tank.

Most importantly, you will need to do your research before bringing fish back home. Aquaria are sensitive ecosystems and their needs will vary greatly according to the type of fish you keep. To know some more, take a look at our step-by-step guide to preparing a cold water aquarium.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to Why Do My Aquarium Fish Keep Dying?, we recommend you visit our Other health problems category.

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