Why do fish die in an aquarium at home?


Why do fish in aquarium suddenly start dying?

Unfortunately, like other living creatures, fish can die ahead of time. Why it happens? The answer to this question is often sought by novice aquarists. It is much more effective to prevent the appearance of such a problem than to look for the causes of a pet's death.

Ideal if you asked this question before the moment the tragedy occurred. Warned, so ready to control all the nuances of the aquarium and try to avoid the early death of aquarium inhabitants. Consider the most common reasons.

Nitrogen poisoning

Nitrogen poisoning is the most common problem. It often concerns beginners who have no experience in dealing with aquarium animals. The fact is that they are trying to feed their pets to the dump, forgetting that with this increases the amount of waste. By the simplest calculations, each fish per day leaves feces equal to 1/3 of its weight. However, not everyone knows that in the process of oxidation and decomposition nitrogen compounds appear, consisting of:

  • Ammonium;
  • Nitrate;
  • Nitrite.

All these substances are united by their toxicity. The most dangerous of them is ammonium, the excess of which will be the main cause of death for all inhabitants of the reservoir. This happens most often in newly launched aquariums. The first week after the start becomes critical. There are two options for increasing the amount of these substances in aqua:

  • Increase in the number of inhabitants;
  • Breakage of the filter;
  • Excessive feed.

It is possible to determine the surplus by the state of water, more precisely by smell and color. If you noted the darkening of the water and the smell of rot, then the process of increasing ammonium in the water is started. It happens that when visually inspected, the water is crystal clear in the house for fish, but the smell makes you wonder. To confirm your suspicions, ask special chemical tests at pet stores. With their help, you can easily measure the level of ammonium. True, it is worth noting the high cost of tests, but for a novice aquarist they are very necessary if you do not want to lose all your pets for a couple of days. If time corrects the situation, then the death will be avoided.

How to lower the level of ammonia:

  • Daily water change ¼
  • Water should stand at least a day;
  • Check the filter and filter element for serviceability.

Wrong launch of fish

Imagine what a fish is experiencing when it goes from one water to another, the parameters of which are significantly different. Buying a fish in a pet store, you deprive it of its usual environment, transferring it to your own, which is completely unfamiliar to the fish. Water differs in hardness, temperature, acidity, etc. Of course, the reaction to such a change will be stress. A sharp change in acidity of at least 1 unit indicates death for sensitive fish. Sometimes the difference in acidity is much more, so the shock that the fish is experiencing can end in death.

Proper adaptation of the fish to the new environment:

  • Pour the water with the fish in a large vessel;
  • Add some water from the common aquarium;
  • After 10-15 minutes, repeat the procedure;
  • Dilute with water to at least 70% solution.

Even if several new fish managed to survive after a crushing change of water parameters, then they will surely die in the first illness. Immunity is significantly undermined, which means that bacteria attack them first. Carefully follow the aeration, cleanliness and new inhabitants. At best, the health of the fish is normalized.

Fish diseases

No one wants to blame himself, so beginner breeders blame the disease. Unscrupulous sellers only reinforce their doubts, because they have a goal to sell expensive medicine and cash in on. However, do not rush for a panacea, carefully examine all possible causes of death.

Blame the disease is possible only if the symptoms have been noted for a long time. The fish died away gradually, and not just died in an instant, for no apparent reason. Most often, the disease is brought to the aquarium with new residents or plants. Death may occur due to malfunction of the heating element in cold weather.

Going to pet stores, you should be aware of what exactly you need medicine. Each of the drugs directed to a specific disease. Universal drugs do not exist! If possible, consult an experienced aquarist or ask a question on the forum, knowledgeable people will tell you what to do in this situation.

Of course, the disease can not kill a healthy fish. Why do fish die in an aquarium? If the death occurred, then the immunity has already been undermined. Most likely, the first two errors occurred. Do not rush to launch new residents, no matter how beautiful they are.

What to do to protect the aquarium:

  • Organize quarantine for new inhabitants;
  • Sanitize fish or plants.

What to do if the disease started up in the aquarium:

  • Change one tenth of the water daily;
  • Increase the temperature;
  • Strengthen aeration;
  • Remove the carriers of the disease and those who are clearly infected.

Remember which fish you ran at home last. Individuals brought from other countries can be carriers of rare diseases, and it is sometimes impossible to detect and classify on their own.

Water quality

Utilities do not set themselves the task of purifying water to such an extent that aquarium residents feel comfortable. Their goal is to make it safe for the person and his home. Hence the popularity of bottled water. Tap water contains maximum chlorine levels. In large cities, there may be a probability of changing water from artesian to desalinated. As a result, water hardness will increase, leading to mass death. You can notice this by the modified behavior of the fish - they begin to rush around the aquarium in a state of horror.

You can avoid this situation. For this:

  • It is not recommended to change at a time more than 1/3 of water
  • Settle the water in an open vessel for at least a day;
  • If possible, purchase a water filter with three secretions;
  • Use chemicals.

Please note that deaths are those fish that were already in a state of stress.

O2 deficiency

This option is the rarest of all. Oxygenation of a fish house is always adequately assessed even by beginners. The first thing they do is buy a compressor. With him, not terrible choking fish.

The only possible option is to increase the temperature and, as a result, lower oxygen in the water. This can happen at night, when the plants are rearranged from the production of oxygen, to its absorption. To avoid this, do not turn off the compressor at night.

Aggressive neighbors

Before you go to the store for pets, think over to the smallest detail, can there be several species in one fish house? You should not rely on the competence of the seller, since the main goal for him is to realize as much of the goods as possible.

A few fundamental rules:

  • Big fish always tend to eat small ones (even in the case of herbivorous species);
  • Many succumb to intraspecific aggression;
  • Some are able to stick to small neighbors, which ultimately leads to death;
  • The strong always eat the weak;
  • Buy only those fish whose peace-loving nature you are sure of.

Unfortunately, it is impossible to establish why fish die. The death of a pet can happen even to experienced breeders. Be attentive to the fish, and you will definitely notice a change in behavior and in time eliminate the cause of anxiety. More often, fish die in an aquarium because of an oversight, and not according to other criteria.

Fish die in the aquarium: reasons

Why die fish in an aquarium?

Sometimes in the aquarium, the fish begin to die one by one. Their owner makes a rash decision - he goes to the pet store and buys any funds offered by the seller. But nothing helps. So, why fish die in an aquarium? There are several reasons for this.

Bacteria - fight!

The main problem of all troubles in an aquarium is dirty water. Beginning breeders, as a rule, forget that the fish not only breathes and eats, but also feces. As a result, the increased content of nitrate, ammonium and nitrite leads to a mora. And the first two are especially dangerous. Poisoning with these substances can be seen with the naked eye: there is a smell of rot, the water becomes cloudy and the question: "Why do the fish die in the aquarium?" can be considered closed.

Bacteria that fight poison and toxins live in the filter media and in the soil. It is important to clean both substrates carefully but carefully. Otherwise, you can destroy the fighters for health. Thus, there is no need to clean the aquarium to sterility and periodically turn off the filter (otherwise anaerobic microorganisms will settle there). By following these simple rules, you can maintain the health of this biosystem and then the fish will not die.
To restore the lost balance, the following instructions are recommended:

  1. Stop feeding for a short period of time. Fish without food can last for several days
  2. Measure the level of toxic substances using special tests (sold at the pet store)
  3. If the readings are equal to 2 ppm, then it is necessary to replace half the water in the aquarium, but gradually, otherwise the death of the fish will not stop.
  4. Follow the second and third points for several days until the microflora is restored.
  5. In no case can not use antibiotics. They are completely destroyed biobalance!

It is important to remember that the aquarium, as a fabulous teremok, can fall apart if it is overpopulated. Fish die because of gluttony. If overfeeding occurs, food debris will simply begin to decompose. Therefore, it is better to reduce the portions than to increase.


As a rule, the temperature, pH and hardness of the water in the pet store is very different from the aquarium breeder. The strongest stress, and therefore the reason why the fish die in the aquarium, can become an ordinary room in a new habitat. Changes in pH can even kill pets or lead to their fatal illness. How to help them endure stress?
First you need to put the bag with the newly purchased fish in the aquarium and attach it with a clothespin to the glass. Then - weak aeration. After 10 minutes you need to pour into the package aquarium water. Repeat this step every 12-15 minutes. After half an hour, you can release the fish in a new home. And finally, the last step - the addition of anti-stress drugs and feeding.

Living water or dead?

If the fish die after the change of water and, moreover on a massive scale, it means that the plumbing companies are to blame. They are usually interested in the health of a person, not his pets. Companies may suddenly change the Ph or the hardness of the water. In addition, it is strongly influenced by the melting of snow.
In this case, it is recommended (especially in spring) to defend water, at least a day. In addition, it is desirable to heat it to 70 degrees, and then gradually cool. Another tip: do not make large changes of liquid (more than 30% of the volume). It is also important to avoid sudden changes in temperature in the aquarium.


Very often, this is the reason newcomers hear from sellers to the question: "Why do I have fish die in an aquarium?", Because the latter are interested in profits from sales of expensive drugs. It is important after the purchase of pets to quarantine, and sometimes - preventive treatment. But even in this case, the fish can get sick. In this case, to prevent the pestilence, the ill person should be placed in a separate aquarium.
Imported fish sometimes bring rare species of disease that cannot be determined without special laboratory analysis. In pet stores there are a lot of drugs that can save pets from misfortune, but it’s better not to be consulted about the choice of treatment from the sellers, but from experienced aquarists. But, as a rule, before treating the problem itself, it is necessary to look for its source: reduced immunity and, consequently, the poor state of the composition of the water.
Fish die from many causes, but the pillars of care for them are unchanged: regular cleaning of the soil and water filtration, timely replacement of water, not overfeeding.

What to do if fish die in an aquarium

Aquarium fish can die for various reasons. The most common are drastic changes in water parameters, disease, and body wear. The detrimental level of oxygen in the water affects the health of the fish. In this case, the fish are at the surface of the water, and capture the air. If the problem is not solved in time, the pets will die. Unfortunately, there are a number of reasons why domestic fish can die.

The level of oxygen in an aquatic environment depends on the temperature of the water (in warm water, a low concentration of dissolved oxygen), chemical indicators, a bacterial film on the surface of the water, outbreaks of ciliates and algae. To solve the problem will help water renewal, intensive aeration. Fluctuations of the surface layer of water play a leading role in the gas exchange of a closed space.

Common causes of death of aquarium fish

  1. Water of inadequate quality (dirty, turbid, toxic). The likely cause of death is poisoning with nitrogenous compounds that are formed after the collapse of fish waste. Improper water purification leads to the fact that nitrites, nitrates and ammonium as toxic substances quickly spread in the water. The correct nitrogenous cycle is a guarantee of the health of all pets. But if the water is poisoned by nitrogenous compounds, it becomes turbid, the smell of rot will appear. The dissolved ammonia can be in a reservoir in high doses at a pH level of 7.5 and above. At lower pH levels, ammonium is not so toxic, but it can harm small fish. Fish die from poisoning with this substance.

  2. Wrong conditions of the settlement of fish, too fast adaptation. Water in a pet store and in a home tank can vary in many ways. If the fish instantly settle into the water of a different pH level, hardness, temperature, with a difference of one unit and more, then they die within 24 hours or one week. It is advisable to take water from the store aquarium in a portable package, and pour it into a separate container. It is necessary to add water from the main reservoir in portions, not more than 5% of the total volume, at intervals of 10 minutes. Fish can be transplanted into the aquarium after the part of the aquarium water in the tank becomes higher than 60-75% of the total volume.

    See how to properly transplant aquarium fish.

  3. Gas embolism is a disease that can lead to the sudden death of a fish. On the eyes, the body can be seen capillaries, the body turns red, the fish swims from corner to corner, the body is covered with air bubbles, the scales are tousled. The disease is the result of a sharp replacement of water (more than 50%), or the settlement of the pet in the water, recruited directly from the tap.

  4. Illness is another reason why fish die. Often the symptoms of the disease are visible immediately by the behavior of the fish and its appearance. Diseases are the result of a weak immune system, stress, infection. Without solving problems with water, even drugs do not always eliminate the problem. Some treatments may not be suitable, and may lead to poor health. For example, salting water for medicinal purposes is impossible if the fish are poisoned by nitrates. Therefore, if you buy a new fish, leave it for a 2-4 week quarantine so that it probably does not bring the disease to the general aquarium. After quarantine, healthy fish can be launched to other fish.

What to do if you find a dead fish in the walls of the aquarium?

  1. Look at the number of fish in the tank. Recount them in the morning and in the hours of feeding. What is their condition, do they take food well? Are there fish that refuse food? Is bloating in one of the fish possible? If you have not found any fish, check all the corners in the aquarium by lifting the lid. Inspect the plants, caverns and all the scenery. If after a few days the dead fish did not float to the surface, it may have suffered from a neighbor in the aquarium, and you can hardly find it. Sometimes the fish fall into an unprotected filter, and die there. In any case, keep searching until you find the visible reasons for the disappearance.

  2. Fish that have died in an aquarium should be removed from it. Tropical species of fish quickly rot because of high water temperature. Under conditions of such an environment, bacteria multiply rapidly, water grows turbid, and an unpleasant odor appears, which can cause infection of other pets.
  3. It is necessary to do inspection of the dead fish. You must understand why she died in an aquarium. Wear medical gloves. If the body is not completely decomposed, look at the condition of the fins, scales, and condition of the abdominal cavity. Perhaps there are wounds on the body or signs that she has suffered from unproductive neighbors. If the stomach is strongly swollen, eyes bulging, the scales are covered with bloom or stains - it means that the pet has suffered from illness or poisoning. После осмотра перчатки нужно выбросить.

  4. Проверьте параметры воды. Вода зачастую является основной причиной ухудшения состояния здоровья рыбы. Возьмите тесты с индикаторами, и сделайте необходимые замеры. Повышенное содержание в воде аммиака и нитратов, тяжелых металлов приводит к тому, что питомцы быстро дохнут. If the aquarium has a decorative element made of iron, zinc, copper - this is another pointer. Some fish do not tolerate metal, and suddenly die.

    Watch a video on why water tests are needed and how to use them.

  5. After the test results, draw conclusions. The test will show two results - either you have everything in order in the aquarium, or the water is dirty and there is an overabundance of toxic substances in it. In the second case, you need to enable powerful filtering, and make a replacement of 25% of the aquarium water for clean and infused. Dramatically change the parameters of the water is not necessary, it can harm living fish.

  6. But if the water is in proper condition, there may be a number of other reasons why the fish died. Sometimes aquarium pets die of hunger, overeating, illness, severe stress, bruises after attacking other fish, age. If the fish die suddenly, you need to do everything necessary to keep others alive. Contact your veterinarian if you do not find obvious causes of death of the pet.

Why die, die aquarium fish?

Aquarium fish - creatures that require increased care and attention. These small creatures of various shapes and colors have one common property - they easily begin to ache and die when they are not properly cared for.

The factors, the non-observance of which leads to the death of the fish, are as follows.

  • Non-compliance with the temperature regime. As a rule, aquarium fishes are thermophilic and prefer a rather narrow range of water temperature, which is individual for each family and specifically for each species. Deviation from it in one direction or another is guaranteed to lead to the death of fish.

  • Insufficient aeration. Aquarium fish, like all the fauna on earth, breathe oxygen from the air, which they take from the water. For some species, insufficient aeration is detrimental and leads to the death of the pet.

  • Non-compliance with water hardness parameters. Incorrectly chosen water hardness is another factor why aquarium fish die. For example, the Bolivian Apistogram is extremely sensitive to this parameter, and the fish that grew in soft water may not settle down in hard water.

  • Increase the level of harmful chemicals in the water. When the aquarium is overcrowded and the proper organization of the aquarium’s care cycle is not organized in water, various kinds of harmful amino and other compounds may be formed that contribute to the death of the fish.

  • Complete replacement of water in the aquarium. Another fatal mistake of novice aquarists, in which the fish die, is a complete change of water in the aquarium, due to which biological imbalance occurs and the likelihood of the disease of the fish increases.

  • Adding tap water to the aquarium. It is not a secret for anyone that water from a water supply system incorporates dissolved chlorine with which it is processed, and therefore the ingress of such “hypochlorous water” is another reason why aquarium fish die.

  • Incompatibility of fish. Most fish are predators, and therefore the compatibility of different families and species in the same aquarium should be taken into account.

  • Overfeeding fish When feeding fish, it is necessary to ensure that the fish do not overeat - that is, give them a limited amount of feed. Otherwise (since these pets do not know how to independently control the food intake), their bellies will swell, and they themselves will be sick and die.

Proper Aquarium Care - Disinfection

Do not forget that the aquarium is a real home for fish. He, like the human home, needs cleaning. If a person can provide himself with cleaning often, then this luxury is not available for fish, so the owner should be engaged in disinfecting the aquarium and monitoring the condition of their pets. Many people know about it, but not everyone knows how to disinfect an aquarium correctly.

Primary events

The first disinfection of the aquarium occurs immediately after you purchase the tank. The future home for fish must undergo a thorough treatment before the first inhabitants of the flora and fauna appear there.

How to carry out the initial disinfection:

  1. Fill the aquarium with plain water.
  2. Dilute the solution of potassium permanganate to a dark color and pour it into an aquarium filled with tap water.
  3. After that, leave it for a day. During this time, all pathogenic bacteria will die.
  4. Drain all the water and wipe dry the walls with a dry cloth.
  5. Rinse it several times with clean running water.

The next step will be the preparation of water for the launch of a new aquarium. To free chlorine out of the water, you must defend all 100% of the water for at least 3 days. Then pour and wait a couple of days. Only after this water will be ready to accept the first inhabitants.

In order not to waste time, prepare the rest of the equipment and decor for your exclusive reservoir. Do not forget, they also need to be thoroughly disinfected before they end up in the same water as the fish. Particular attention is paid to the ground. As it is most often used sea sand and pebbles collected in natural conditions. Of course, in the substrate collected a huge number of pathogenic bacteria that will poison the entire environment in the water. To defeat the negative consequences you need to ignite the soil in the oven or in a large frying pan. Exposure to maximum temperature should be all the soil and at least 20 minutes. For convenience, divide it into portions. Do not put the hot sand in the aquarium! Cool and rinse thoroughly. One washing is not enough, it is better to repeat the procedure 3-4 times, only after that you can put it in the aquarium. Do not ignore this stage of the initial launch of the aquarium.

Among the mandatory elements of the normal functioning of an artificial reservoir are accessories. Collect all the elements of the decor, excluding plastic options and boil them thoroughly. Since plastic parts can melt from heat treatment, it is better to process them with a dark solution of potassium permanganate.

Disinfection Flow Measures

In the event that the aquarium is already functioning, but a nuisance has happened and various bacteria and algae have begun to appear in it, then disinfection cannot be avoided. It is urgent to save plants and fish from there.

All the fauna that was in the infected aquarium should be treated with an antibacterial solution. The most popular is a mixture of 10 mg of penacilin per 2 liters of water. Soak plants in it for about 3 days. Do not be afraid, nothing terrible will happen to plants during this time. The aquarium itself can be disinfected with a special bactericidal lamp every day for 20 minutes. Aquarium disinfection is necessary even if there are no visible problems. Preventive measures are the best way to maintain the health of fish and other inhabitants. The next disinfection begins with a disinfecting treatment of all surfaces. The simplest available tools are potassium permanganate and peroxide. Remove from there all the fish and decor, then fill to the edge with 3% peroxide or dark solution of potassium permanganate. Leave everything for 5-6 hours. After that, thoroughly rinse all surfaces and corners.

If so much time to wait there is neither time nor desire, then you can use the express method. Buy a special solution at the pet store that is designed to disinfect all surfaces. Remember to wear gloves before handling. If you have the opportunity to process all formalin, chloramine, hydrochloric acid - then use this option.

To disinfect plants, it is necessary to prepare a penicillin solution in a ratio of 10: 2. Leave all the plants there for about three days.

The most common means are:

  • Isopropane 70%;
  • Ethanol 70%;
  • Saydeks;
  • N-propanol 60%.

These tools can wipe the plants just one time, this will be enough to kill the pathogenic sphere. Sell ​​these funds in pet pharmacies. The rest of the inventory should be boiled. For fidelity, keep them in boiling water for at least 20 minutes. The more time they spend in boiling water, the less chance the bacteria will survive. Note, rubber, plastic and thermometers can not be boiled in any case.

Choose the most convenient way for yourself and enjoy the view of a beautiful, healthy aquarium with happy fish.

Why die aquarium fish? What to do?


You have a good set of fish, it turns out, there are quite a lot of them. Maybe. xilorodane is enough, for 1 cm of fish there should be 2 liters of water, with a constantly working aerator it can be reduced to 1 liter. Water as you defend? Stress is possible when transplanting to an aquarium, even if your conditions are better than those in which the fish used to live, all you need to do is give them the opportunity to get comfortable with it for about 10-20 minutes. They should be lowered into the water gradually, so that the shock does not occur due to a change in temperature, water hardness, etc. The temperature is very important, for your fish 24-28.
In general, the death of fish is a common thing for a beginner, my first two months were also constantly dying. Gain experience and everything will be fine. The main thing is not to despair and not to give up such a good thing as aquarist!
Correctly spelled - mollies.


Maybe one of the fish was infected and the other infected. Seat all the fish in separate jars, let them sit for a couple of days and change the water in the aquarium. You can buy specials. solution that kills the disease and add to the water. Contact your nearest pet store, they will advise you what to do and how.

Tatyana Komarova

Do not buy plants, they are infected with sores. from which the fish die. You can purchase a solution of "blue" in the pet store, drip 10-15 drops. Or at the very least, to purchase both fish and plants, all together, not separately !!!!


Check the temperature, oxygen, water PH - special indicators are sold in pet stores. Calculate whether your aquarium is overpopulated - sometimes the fish die from lack of space, personal territory.
If before the death of the fish you have someone hooked up - an infection is possible. If there are no more accurate symptoms, buy generic drugs (although this is not the best option).
In addition, since the aquarium is only a month old, the microflora and the environment are still normalizing. I was with the first aquarium population.


Have you defended water directly in aqua for 3-4 days? Perhaps due to the toxicity of glue this happens. In general, it is necessary to prepare an aqua to launch fish for about 2 weeks or buy special products in stores that speed up the process of becoming a normal aquarium environment ... Read on the forums ...
Now I advise you to re-wash, and it is better to boil the soil, re-defend the water in aqua 5 days and run the fish ...
In general, it is strange - you had unpretentious fish ...

Elena Grigorieva

For beginners, this is a common situation. My first two aquariums grunted, then I treated the fish for a long time, when everything settled down, the problems disappeared. First, check whether the tails and fins of the fish are visually clean, if there are any blotches, this is a disease. Even if the water is defended when the water is poured into the aquarium, air bubbles appear on the walls. bubbles on the walls will not disappear, if they plant algae, they are planted before running the fish, but I refused to live algae, I have an artificial low-cost and it’s not a bad thing to throw it away, but they look like real ones. Do not transport fish in cans, there are special bags that are pumped with air when you bring them home. Put the preparation of Stres Zoom in the container. It helps to transfer stressful situations to fish and restores the skin damaged during transportation. When you transplant fish from the tank to the aquarium, you need to equilibrate the temperature. Good luck.

Why do fish - tail fish die in the aquarium after 2 months, the rest live for a long time.?


Perhaps the wrong conditions of detention and feeding. The veiltail is one of the artificially cultivated decorative breeds of the aquarium "golden fish" which is known for its elongated fins and longer, fluffy veil tail - in comparison with other representatives of this species.
They are satisfied with any food, not too demanding to the conditions of detention, calm and beautiful. With good care, goldfish live up to 20 years.
Peaceful in nature, peaceful goldfish, Veiltails get along well with the same calm neighbors, but it is preferable to keep only ornamental forms of goldfish in one aquarium. Keep goldfish - voilehvostov need in a spacious high aquarium with a volume of at least 50 liters per fish, it is better if it is an aquarium of at least 100 liters, which will place a couple of fish. If you increase the size of the aquarium, the population density can be slightly increased, so 3-4 fish can be placed in an aquarium of 150 liters, and in 200 liters - 5-6, etc. But if you increase the density of the population, you should pay attention to good aeration of water. These aquarium fish love to dig in the ground, so as it is better to use pebbles or coarse sand, then the fish will not be so easy to scatter. The aquarium itself is desirable species and spacious, in which to place large-leaved aquarium plants.
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