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Nitrite in the Aquarium (Danger)! Just about Complex! Learn First!

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Nitrite (NO2) is another invisible chemical enemy of living things in an aquarium. Nitrites are formed with the help of beneficial bacteria living in the filter and soil of our aquarium. Using oxygen, bacteria oxidize ammonia, turning it into chemical compounds called “nitrites” and the formula (NO2).

Nitrites (NO2) are direct descendants of ammonia and are just as deadly for fish in excess of normal concentrations.

Nitrite (NO2) at the aquarium tests can bee seen on this image. The nitrite test in the aquarium can be seen in this image.
Nitrite (NO2)

Nitrites. Symptoms of poisoning.

Symptoms of nitrite poisoning are very similar to those of fish poisoning with ammonia:

1. Fish become sluggish.

2. Hold to the surface of the water.

3. They gasped for air.

4. Refuse to eat.

5. Very often they breathe.

All these signs are very similar to the lack of oxygen in the water. But how can this be, if, for example, a compressor for supplying air to an aquarium is operating at full capacity?

The fact is that with nitrate poisoning, the fish begins manifest "Brown blood syndrome". When nitrates provoke elevated levels of methemoglobin in the blood. Because of this, the blood acquires a brown tint. But the most terrible and dangerous thing is that it also loses the ability to transport oxygen to the organs. And the fish begin to choke, even in an oxygen-filled aquarium.

Nitrites (NO2) are the causes of increased doses in the aquarium.

As with any chemical poisoning caused inside the aquarium, the most common cause of poisoning with nitrites, like ammonia, is the violation of the chemical (biological) Balance in aquarium. Such a violation is usually cited:

1. Too frequent and thorough cleaning in an aquarium with a siphonize of soil.

2. Frequent cleaning of internal filter media.

3. Flushing the filter in tap water.

3. Large and frequent substitutions of the water in a new aquarium.

4. Treatment with medical products.

5. Overpopulation of the aquarium.

6. Overfeeding of fish.

7. Insufficient aeration of water in the aquarium.

All these actions will ultimately lead to either death or an insufficient amount of nitrifying (Nitrosomonas) of bacteria. There is simply nobody to process nitrites, and they will start poisoning everything in the aquarium.

⚠ It seems to the aquarist that the cleaner the aquarium filter and the soil, the better. But, in fact, everything is exactly the opposite. Wash the filter and siphonate the soil as little as possible, otherwise you will constantly wash out useful bacteria, have a high level of ammonia and nitrites, and as a consequence, sick fish.
For example, in a large aquarium filter, I regularly change only the sintepon for mechanical cleaning. And the rest of my sponge is 3-4 times a year. And better, do not wash the filter along with changing the water, as everyone usually tries. And wait another day and keep the balance in the norm.

Nitrite in the aquarium. Methods of determination and acceptable standards.

Visually, we can understand that nitrites are elevated only by the behavior of the fish. This is bad and it may be too late. Therefore, it is desirable to have in your arsenal tests nitrites in aquarium. No matter what manufacturer. They have almost all. The principle of determination among different manufacturers of tests may differ, but the result will be similar. Compare readings from the aquarium water taken, and compare the color of the liquid with the color scale.

Perfect result for Nitrite (NO2) for aqurium water can be seen in this foto. Nitrite in the aquarium with excellent indicators can be seen in this photo.
Great Test Result!
Nitrite (NO2) tests for aquarium can be seen in this image. The nitrite test in the aquarium is shown in this image.
Valid Test Result!

Nitrites. Permissible norms.

A better result would be a result near zero. Ideally, nitrites should not be detected by tests at all. Increased concentration is permissible only in recently launched aquariums. (How to start the aquarium, and avoid increasing ammonia and nitrates, read on this link.) The acceptable norm, according to some manufacturers, is 0.2 mg / l. Anything higher is already dangerous.

What to do if you do not have tests for nitrites, but there are tests for ammonia. And they show its elevated level, then the level of nitrites will most likely be overestimated. Or rise after some time. But for us this is not particularly important, since the methods for solving the problem will be the same.

Nitrites. Methods of elimination.

1. The most emergency method - Replacement of up to 50% of water with tap water. But this method is not suitable for newly launched aquariums, because you will “kill” an already unbalanced balance. But if you have several aquariums, or someone can share with you some water from the "old" aquarium with zero readings for nitrite tests, then it will be just wonderful. You will not only lower nitrite levels, but also add beneficial bacteria to your aquarium.

2. Addition zeolite into the filter. This method is not as fast, but it will reduce ammonia in the water. And with it, the nitrites will go away.

3. Addition of aquarium salt (sodium chloride) in the aquarium. For example, API AQUARIUM SALT (instruction - link). Salt will help reduce nitrite levels and ease fish breathing.

4. Adding special tools with colonies of living bacteria. Here are some of them.

- Tetra "Cleaning Bacteria " - link.

- Tetra "Start Zyme " - link.

- JBL "Denitrol " - link.

- Sera "Bio Nitrivec " - link.


In order to win nitrites in the aquarium, we will most likely have to first remove the elevated level ammonia and set up a bio balance.

And how to do this, read below:

Ammonia in the aquarium! What to do?

Balance in the aquarium!

Filtering in the aquarium!

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Nitrite (NO2) at the aquarium.
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