How To Get Rid of Nitrite in Fish Tank

nitrite in fish tank

Nitrite is a waste product developed during the biological filtration process. This nitrite can cause severe harm to the fishes present in the fish tank and at times can even kill them. It is regarded as the most lethal byproduct and requires immediate checks. When the fish gives out ammonia, this ammonia further changes to harmful nitrite. If there is a proper biological filter present, this nitrite gets converted into harmless nitrate.

However, even this harmless nitrate should be done away with since this can give rise to high nitrite and poison the fish.

Now to know how to lower nitrite in a fish tank, one needs to have a good understanding of the reasons responsible for high nitrate.

Reasons for high nitrite in the fish tank

The first crucial reason for high nitrite is that whenever a new aquarium is set up, it requires more time to develop the beneficial bacteria for fixing nitrite in a fish tank.

The second reason can be an inferior biological filter which is, thus, not able to convert the harmful nitrite into harmless nitrate.

The third reason is that too many fishes or large fishes are put in the container at once, thus, causing hindrance in the working of the bacteria.

The fourth reason is mainly the overfeeding of the fishes, which excrete more and thus, produces more ammonia in the fish tank. This ammonia production is the initial stage in the development of nitrite.

The fifth reason is the dry-cleaning of the tank and changing its water more often. This way, the beneficial bacteria get washed away from the water and can no longer prevent the increase of nitrite in the fish tank.

Now, as we know the reasons for high nitrite, we can discuss the symptoms of increasing nitrite in the fish tank.


An increase in the level of nitrite in the fish tank can also lead to the development of a fatal disease that is nitrite poisoning. This disease can result in the death of the fish. Thus, it is crucial to learn about the primary symptoms of nitrite presence in a fish tank.

  • Firstly, nitrite usually causes nitrite poisoning among the fishes, which then turns the gills of the fish brown. Thus, it is called Brown Blood diseases.
  • Secondly, nitrite poisoning increases methemoglobin in the blood of fish, reducing its oxygen-carrying capacity. Thus, the fish move towards the top of the tank to breathe properly.
  • Thirdly, the fish becomes quite list-less, and due to suffocation, it moves near the outlet of the fish tank.
  • Fourth, the fish’s gill movement becomes faster.
  • Fifth, methemoglobin causes liver disease, gill diseases and damage to blood cells. It even causes itching, fin rot, and bacterial infections.

How to reduce nitrite in the fish tank

A nitrite level below two ppm is considered harmless. However, when it goes above two ppm, it can also cause the death of the fish.

  • Changing the water in the fish tank partially every week can be very beneficial in checking nitrite development in the fish tank. This way, the concentration of nitrite is diluted in the water.
  • One can also purchase bottled bacteria from Since a new tank is unable to complete the nitrogen cycle, one can always add nitrifying bacteria in the water so that the increased nitrite remains checked. Also, it is essential to know the proper dosage required for this. API Quick Start Nitrifying Bacteria for Freshwater and Saltwater Aquariums are readily available at Amazon.
  • A good filter is also very essential for checking of the nitrite level in the fish tank. A good filter increases the oxygen level in the fish tank and develops an ample amount of beneficial bacteria. This way, the fish is no longer left to suffocate in the fish tank.
  • One can also use the biological filter from an established and old tank as its bacteria had already developed.
  • Now, a very significant part of the lowering of nitrite in a fish tank is a nitrite test. In a new container, the nitrite test is recommended. Also, restrain from adding extra fishes in the tank, when the filter is not working properly and while the medication of a fish is being done.
  • Now, adding marine salt that is sodium chloride can also be beneficial in checking nitrite in the fish tank. By dechlorinating water, it decreases the nitrite volume in the tank. Add only half tablespoon of this salt in one gallon of water as it is enough for reducing the methemoglobin thus, helping to protect the fish from nitrite.
  • It is advisable to prevent overfeeding of fishes to avoid the increase of nitrite, which is developed through the fish’s excretion. In case a fish is already suffering from nitrite poisoning, it is recommended not to feed it for several days, until the poisoning it done away with.
  • Even the leftover food of the fish tank should be cleaned in no time.
  • Now, adding too many fishes at once can also be dangerous. At the time when the fish tank is newly set up, it will not be able to develop enough nitrite fixing bacteria. Thus, only two fishes should be put at this time. Even though the tank becomes well established, one should not put more than two fishes at once. Also, when a fish is being treated for nitrite poisoning, no new fish should be added in the fish tank.

Therefore, by developing an understanding of these, we now know how to get rid of nitrite in fish water. Since ammonia development is the initial stage of nitrite development, it is equally important to remove ammonia and nitrite. Also, nitrite can even cause the death of the fish, so it is crucial to have a check on its increase. Nitrite is responsible for the occurrence of a fatal disease called nitrite poisoning in the fish which can cause severe damages of its liver, fins, gill, and blood cells and at times, even lead the fish to succumb to death. Thus, one should do nitrite test in the fish tank so that the fish doesn’t die of suffocating and any amount of nitrite in the tank remains unchecked.

Therefore, we have discussed the entire detail related to nitrite levels in the tank. From the reasons for nitrite development to the symptoms and process of lowering nitrite in the fish tank.