Why Is My Fish Tank Cloudy After 1 Day or 2 Days?

Cloudy water in the fish tank at the start-up stage even after 1 day is an absolutely natural phenomenon that does not cause anxiety for experienced aquarists. But newcomers start to panic, change the water, and make chemicals, which only aggravates the situation.

Fish tank cloudy after 1 day is a temporary stage that should just be waited out, the main thing is not to harm, and not to turn the maturation process of the aquarium into a real problem.

why is my fish tank cloudy after 1 day

What is cloudy Water in Fish tank?

When the aquarium is filled with water, the water remains almost transparent, except for slight dust from the ground.

But at the end of 1 day or on the second day, many aquarists observe that it has become cloudy, and sometimes so much that it is almost impossible to see anything.

This process is due to the active reproduction of beneficial bacteria, which will become the basis of biological balance in the underwater world. They will recycle the waste products of the inhabitants, making the water suitable for life.

This phenomenon can persist from several days to a week, and this is absolutely normal, but only if the aquarium has been started in accordance with all the rules.

Is cloudy aquarium water dangerous?

The cloudy water itself does not pose any danger to the biological system of the aquarium and to the plants. But the nitrogen cycle in such an aquarium has not yet started, so there will be a large amount of ammonium/ammonia in the water, and then nitrite, which have a toxic effect on the fish.

is cloudy aquarium water dangerous

That is why experienced aquarists do not recommend putting fish in a freshly launched aquarium. It should take several weeks before the aquarium “cycles” and the water becomes habitable for the inhabitants.

It is worth worrying only if the owner, out of inexperience, released fish or shrimp into a barely running aquarium. This is a huge threat to their lives.

No matter how sellers in pet stores or manufacturers of biostarters (bacterial additives for an aquarium) assure, the nitrogen cycle is fully launched in a month, therefore, it is absolutely impossible to settle fish in the first days. Especially – gentle and demanding species.

why is my fish tank cloudy after 1 day or 2 Days?

There can be several reasons for the fish tank cloudy after 1 day, among them, there are both classic and natural processes, and abnormal ones that occurred through the fault of the aquarist. In some cases, only patience is needed to normalize the situation, but sometimes decisive action is indispensable.


The main reason for the appearance of cloudy water is a bacterial outbreak.

This is the case when you should not worry. The main thing is not to prevent bacteria from multiplying, and not to take unnecessary measures.

In just a few days, everything will return to normal, and the water will become clear.

What to do:

  1. Make the first substitution no earlier than 10 days after launch.
  2. Use high-quality fillers for biological filtration (foam glass, lava, special substrates), which will become a habitat for beneficial bacteria.
  3. Introduce some bacterial cultures, which will speed up the process and make it more “soft”.

Gravel or substrate

Aquarium Soil is the main biological filter of the system. In a healthy aquarium, the amount of bacteria that lives in the soil will never compare to the amount in the filter. Therefore, the choice of soil should be taken seriously.

Poor quality soil, which is not of natural (natural) origin, can release poisons into the water, killing bacteria, which only exacerbates the situation. In addition, the soil has another important nuance – it affects the acidity of the environment.

Limestone soils make the water alkaline, quartz soils make it close to neutral, and special soils make it acidic. Alkaline water is more suitable for bacteria, so they develop much more slowly in an acidic environment.

What to do:

  1. Use only natural soils, unpainted, of natural origin, giving preference to smaller fractions.
  2. In the case of using nutrient soils (soils), run the aquarium as recommended by the manufacturer.
  3. If low-quality artificial soil was used, it is worth restarting the aquarium. Since it will negatively affect not only the balance in the aquarium, but also plants and fish.

Overfeeding fish

After a few weeks, aquarists release the first tenants. After 2 weeks, the danger of poisoning had already passed, the nitrogen cycle began to work. But it is important to remember that this is still a “newly launched” aquarium and the biological balance has not started to work at full capacity.

Therefore, when the owner feeds his pets, he should do it in minimal quantities. Otherwise, uneaten food will start to rot and release poisonous ammonia/ammonium into the aquarium.

That will provoke another stage of mass reproduction of bacteria and, as a result, the water will become cloudy again. The same can be said about the use of low-quality feed.

What to do:

  1. Feed the fish once a day with the amount of food that they can eat in two to three minutes.
  2. It is better to immediately remove uneaten food from the aquarium with a siphon.
  3. Feed only high quality food.


It is worth populating the aquarium gradually, because if you suddenly start a large number of fish, the biological system may not withstand such a load.

Do not forget that fish produce waste, a lot of fish lot of waste.

The small amount of bacteria is unable to cope with the excessive amount of waste products, and another bacterial outbreak occurs. The water becomes cloudy again.

What to do:

  • populate fish little by little;
  • prevent overpopulation;
  • if an outbreak has already occurred, then the fish should be transplanted into a healthy aquarium, since an imbalance can lead to disastrous consequences;
  • when settling fish, increase aeration.

use of chemicals

The use of any chemicals at the launch stage is strictly contraindicated. The exception is fertilizers, and then, in the minimum dosage.

The fact is that most chemical aquarium products negatively affect the biological balance in the aquarium.

Most often, aquarists kill the balance with:

  • glutaraldehydes (Sydex and its derivatives);
  • medicines for fish;
  • products for clear water – as a rule, they greatly lower the acidity of water (pH), which has a detrimental effect on a colony of beneficial bacteria.

It is permissible to use all the above means only in a mature aquarium in which the nitrogen cycle is fully formed.

What to do if the chemical has already been used, and cloudy water has appeared:

  1. Use activated charcoal as a filler.
  2. Make a change of about 30%. In this case, it will not harm the bacteria, since there is no one to harm.
  3. Increase aeration.
  4. After a few days, remove the carbon from the filter.

how to prevent cloudy water in fish tank?

Getting rid of cloudy water is a rather dreary process. cloudy water is easier to prevent than to get rid of.

how to prevent cloudy water in fish tank

All that is required is to follow the basics of a proper launch and not rush. Aquaristism generally does not like haste, especially when it comes to the biological balance in the aquarium.

To prevent the appearance of cloudy water, the following recommendations should be followed:

  1. Run the aquarium only on natural soils.
  2. Immediately from the moment of start-up, use filtering equipment, which must work around the clock. It is important that the filter matches the volume of the aquarium and contains high-quality fillers.
  3. Using biostarters, will not speed up the process of establishing the nitrogen cycle, but will prevent the water from becoming cloudy.
  4. Do not use tap water without settling or using conditioners. Chlorine, which is contained in tap water, is detrimental to bacteria.
  5. It is necessary to populate the fish no earlier than two weeks after the launch. Shrimp or delicate fish species – not earlier than in a month.
  6. Feed moderately only high-quality food.
  7. Changes should be done in minimal quantities. The first replacement not earlier than 10 days after launch, and not more than 20% of the aquarium volume. In the case of using nutrient soils, follow the manufacturer’s recommendations.

By following these simple rules, cloudy water will not be a cause for concern. It is just necessary to remember that the aquarium becomes fully viable only after a month, until this moment it cannot be overloaded, because biological balance is the basis of any aquarium.


The formation of the biological balance of the aquarium is most affected by its correct start. Therefore, the most important thing is not to rush and do everything wisely, following these recommendations. First sort out the reasons why is my fish tank cloudy after 1 day then take action.

A properly run aquarium has a more flexible biological environment and will be able to forgive the non-blunders of the owner. Also, a proper start-up is a key to a healthy aquarium for many months, if not years.

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