fish dying in aquarium

Why are my fish dying in my new aquarium

What to do if you find a dead fish in your new aquarium?

Suddenly you discovered that your fish has died in your aquarium and you don’t know what to do now? I have put together five tips for you to cope with the death of fish and what to do if this does happen. But, remember that even in the most ideal conditions, they still die. Often suddenly, for no apparent reason, and very annoyingly for the owner. Especially if it is a large and beautiful fish, such as cichlids.

First of all, check how your fish breathe!
Often aquarium fish die due to the fact that the parameters of the water have changed. Low oxygen levels in the water affect them most destructively. The characteristic behavior is that most of the fish stand at the surface of the water and swallow air from it. If the situation is not corrected, then after a while they begin to die.

Moreover, such situations can occur even with experienced fishkeepers! The oxygen content in water depends on the temperature of the water (the higher it is, the less oxygen is dissolved), the chemical composition of the water, the bacterial film on the water surface, the outbreak of algae, or ciliates. You can help with partial water changes by turning on aeration or directing the flow from the filter close to the water surface. The fact is that during gas exchange, it is the vibrations of the water surface that play a decisive role.

Take a closer look

Check and count your fish daily while feeding. Are they all alive? Is everyone healthy? Does everyone have a good appetite? Six neons and three catfishes, all in place?

If you missed someone, check the corners of the aquarium and lift the lid, is it somewhere up in the plants? But you may not find the fish, it is quite possible that it died. In this case, stop searching. As a rule, a dead fish still becomes visible, it either floats to the surface, or lies on the bottom, the floor with snags, the stones, or even falls into the filter. Inspect the aquarium every day for a dead fish? If found, then….

Remove dead fish

Any dead fish, like large snails (such as apple snail or marisa), should be removed from the aquarium. They rot very quickly in warm water and create a breeding ground for bacteria, the water becomes cloudy and starts to stink. This all poisons other fish and leads to their death.

Inspect a dead fish

Don’t be scared if you still want to ask the question why are my fish dying in my new aquarium then you have to do it.

If the fish is not yet too decomposed, then do not hesitate to examine it. This is unpleasant but necessary. Are its fins and scales intact? Maybe it’s neighbors beat her to death? Are the eyes still in place and are they not cloudy? Is its belly swollen like in the picture? Maybe she has an internal infection or it was poisoned with something.

Inspect a dead fish

Check the water

Every time you find a dead fish in your aquarium, you need to check the quality of the water using tests. Very often, the reason for the death of fish is an increase in the content of harmful substances in the water – ammonia, and nitrates. To test them, purchase water tests in advance, preferably drip tests.


The test results will show two results, either everything is fine in your aquarium and you must look for the cause in another, or the water is already quite polluted and you need to change it. But, remember that it is better to change no more than 20-25% of the volume of the aquarium, so as not to change the conditions of keeping the fish too dramatically.

If everything is in order with the water, then you need to try to determine the cause of the death of the fish. The most common: illness, hunger, overfeeding (especially with dry food and bloodworms), prolonged stress due to improper housing conditions, age, attack by other fish. And a very common reason – and who knows why … Believe me, any fishkeeper, even one who has been keeping complex fish for many years, has sudden deaths in the tracks of favorite fish.

If the incident is an isolated case, then do not worry – just make sure that new fish do not die. If this happens all the time, then something is clearly wrong. Be sure to contact an experienced fishkeeper, it’s easy to find now since there are forums and the Internet.

Why do my fish die in my new aquarium

It is very unpleasant when fish begin to die in the aquarium. It would seem that everything was done correctly: clean water is poured, the aquarium equipment is working, the fish receive food on time. Despite this, living creatures die.

Unfortunately, this situation occurs quite often among newcomers to the aquarium business, which is why it is necessary to arm yourself with the knowledge of the causes of this phenomenon. Every novice aquarist should understand in advance the following: if conditions are created for its fish in a new aquarium that are as close as possible to their natural habitat, then they will not get sick, let alone die.

At the very least, the risk of death will be minimized.

Practice shows that in the overwhelming majority of cases the death of fish is caused not at all by some external diseases, but by mistakes in the caring, illiteracy, and carelessness of their owners. There are various reasons for this unfortunate phenomenon or a combination of reasons and factors that should be considered in detail.

Poor aquarium water quality

Cloudy aquarium water This does not mean that the water is very dirty or cloudy. No, it can be relatively clean, but poisoned by toxic chemical compounds that are formed as a result of the vital activity of fish.

Harmful chemistry

We are talking about nitrogen compounds, which include ammonia, ammonium, and other nitrates. These toxins will inevitably be present in the aquarium, as fish leave behind a lot of waste every day that is constantly decomposed.

Thus, the visual purity of water is often accompanied by the appearance of an unpleasant smell of rot, which indicates a high concentration of toxic nitrogen compounds.

This smell is especially clearly felt if the aquarium is overcrowded and the biological water purification system cannot cope with the processing of toxins. As a result, the fish gradually begins to poison and subsequently dies.

This state of the aquarium water is formed in the following cases:

  • ecological balance has not yet been achieved in the new aquarium;
  • beneficial bacteria that convert toxic nitrites into neutral nitrates are not yet working at full capacity;
  • new fish have been added to the working balanced aqua system;
  • overpopulation of the aquarium;
  • biofilter malfunction;
  • improper maintenance and cleaning of the biofilter, resulting in the destruction of the colony of beneficial microorganisms.

Based on this, certain measures are taken to prevent water poisoning. This can be either replacing part of its volume, or installing a new biofilter, or resettling excess fish.

Water parameters and launching fish into the aquarium

Water parameters in the aquarium Poor quality of the aquatic environment also mean an imbalance in the pH balance and an inconsistency of water hardness with the usual conditions of aquarium pets. You ought to check this article before so you would have questions like why are my fish dying in my new aquarium or how long to dechlorinate water for fish.

It is not uncommon for a person to bring a fish that they just bought from a pet store and immediately release it from the package into their aquarium, without thinking at all that the pet may experience a natural shock from the discrepancy in the parameters of the environment. And as a result – death during the next day.

Therefore, it is necessary not only to know the exact conditions of keeping this or that species but also to clarify the parameters of the water in the pet store with the seller. And if necessary, organize the adaptation procedure for a new fish.

Water temperature

The death of fish can also occur due to a decrease or increase in the temperature of the aquatic environment. The opinion that a deviation from a certain temperature regime by 2-3 degrees in one direction or another will not affect the health of aquarium pets in any way is deeply mistaken. If the temperature drops, there is a danger of death from a cold, and if the temperature rises, the fish may die from a lack of oxygen.

Lack of oxygen as a negative factor

Why are my fish dying in my new aquarium? Fish are known to breathe oxygen dissolved in water, and they can suffocate if there is too little of it in the aqua. Although such cases are very rare, they do happen.

As a rule, even beginners pre-purchase all the equipment necessary for the operation of a home aqua system.

And very often, when buying a sufficiently powerful filter, they trust him not only for water purification but also for its aeration and mixing.

Still, experts recommend separating these two functions and ensuring the constant operation of the air compressor.

The aggression of neighbors in the aquarium

Even if a large fish is considered herbivorous, it can easily eat small animals that fit into its mouth. In many inhabitants of the domestic reservoir, the degree of aggression increases many times over during the spawning period.

There are aggressive fish due to their natural characteristics, whose bites and blows are very painful. All of these factors can also lead to the death of aquarium pets. Pets like siamese fighting fish.

When buying this or that fish, do not rely entirely on the opinion of the sellers. As a rule, the most important thing for them is the fact of sale.

It’s better to take the time and find out more about the compatibility of certain species even before going to the pet store. Thematic information on this matter on the Internet is quite enough.

Feed quality and overfeeding

Feeding Your Aquarium Fish Many aspiring fishkeepers strongly believe that giving your fish a pinch of dry commercial food every day is sufficient. Far from it.

Continuous feeding of the same dry food can cause the death of animals from inflammation of the stomach or intestines.

It is enough to imagine what will happen to the human body if it constantly, day after day, eats the same dry food!

The diet of the overwhelming majority of fish should be varied, include both protein and plant foods.
Overfeeding is a very common cause of illness and death of living creatures. There are two essential points here. By itself, overfeeding can lead to diseases of the internal organs. In addition, food residues, settling on the ground and gradually decomposing, contribute to a sharp concentration of nitrogen compounds, a large dose of which is fatal for the underwater inhabitants of the aquarium.

Illness – the most common cause

This is true, but in this case, two main factors must be distinguished.


Firstly, the disease can arise as a result of all the reasons listed above. Any of them, if they do not kill the fish immediately, will contribute to a sharp decrease in immunity. On this basis, a disease can develop that can lead to death. If this happens, then the pets should be treated by contacting specialists.

Secondly, the death of fish can be caused by the development of infectious diseases. This is the worst case scenario when maintaining an aquarium. Why do infectious diseases appear? As a rule, there are two main reasons: the introduction of already infected fish into the aquarium or the appearance of parasites in the water house. Fungal diseases, peptic ulcer, Ichthyophthirius, tuberculosis, and many other infections can cause not only the death of an individual but also massive death.

It is necessary to monitor the behavior of aquarium pets every day, carefully examine them, and in case of the slightest suspicion, move the diseased individual to quarantine and consult a specialist.

Unfortunately, almost every fishkeeper will have a pet die at least once. And the reasons can be completely different. It is important to thoughtfully analyze the incident that happened, identifying a specific cause, and try to prevent it from recurring. I hope you got a good answer on why your fish are dying in your new aquarium. And if knowledge and experience are not enough, there is the Internet and advice from experienced ornamental fish owners.