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Nitrates in the Aquarium (Dangerous NO3): Just about Complex! Personal experience!

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Nitrates (NO3) in an aquarium, this is the last representative in the chain of chemical compounds of the nitrogen cycle. About the previous two, much more dangerous and hidden killers in the aquarium, read in my posts, the links below.

Ammonia in the aquarium! Danger!

Nitrite in the aquarium! Danger!

This photo shows the chemical balance that occurs in the aquarium. Chemical balance can be seen on this picture.
Chemical processes in the aquarium!

Nitrates are less dangerous than ammonia and nitrites. And unlike nitrites, the norm for which is not more than 0,2 mg / l, a dangerous concentration of nitrates starts from 50 mg / l. But even in excess of concentration they can cause a lot of trouble in the aquarium, both for fish and plants. They are formed as a by-product from the processing of nitrite by bacteria. And in small concentrations they are even useful, since one part of them serves as food for plants. And the second, with the help of other bacteria, turns into a gaseous form of nitrogen, and is removed from the aquarium. But there are several negative points in this process.

Nitrates. Negative moments!

Firstly, if plants do not have time to eat nitrates, then algae will gladly take their place. And your aquarium will quickly become covered with an undesirable green coating. To deal with which later will also be not very pleasant. Of course, ideally, you can achieve equilibrium in the aquarium, in which all nitrates will be absorbed by plants. But for this they must be very many and very few fish. Which is not always feasible, especially for beginners.

Secondly, bacteria need a lot of oxygen to process nitrates with bacteria. They are called aerobic bacteria. Which, translated from Greek, means organisms that need free oxygen. And if there is usually enough oxygen near the surface of the soil or in the filter, then with every centimeter of depth, it is less or less. And then, if beneficial bacteria did not manage to process all nitrates, other “evil” bacteria, which are called anaerobic, come into play. Which, judging by the name, does not need oxygen at all. And they begin to process nitrates back into dangerous nitrite!

Such a cycle of dangerous chemistry in an aquarium occurs in seemingly crystal clear water!

Nitrates in the aquarium. How to determine?

Unlike ammonia and nitrites, which can be recognized by the behavior of fish, nitrates are becoming more complex. Visually, you may not notice anything, but your fish will be under constant stress because of them and their immune system will suffer. And if nitrates are constantly kept at a high level, then your fish gradually develop addiction to them. But the new tenants planted in your aquarium do not have such protection. And most likely they will die after some time, for no apparent reason ..

The best way to avoid this situation is to use nitrate tests in a timely manner.

Nitrates. Tests and norms.

The fact is that nitrates are present even in tap water. With acceptable standards for it, usually <10 mg / L. Therefore, for 100% reliability of the test results, you must first test the water from the tap, then from the aquarium, and then compare the readings.

Different types of fish have different sensitivity to nitrates. The extreme upper limit of safe tolerance is 40-50 mg / L. Although with a smooth increase in fish, they can even 400 mg / l. But all experts agree that nitrates should be kept at the lowest possible level.

Nitrate test NO3 can be seen in this picture. The nitrate test in the aquarium is shown in this image.
Nitrates: Test!

How to reduce the amount of nitrate in the aquarium?

Substitution of part of the water.

As with any undesirable chemical compounds in the aquarium, the simplest and fastest way is to replace some of the water with fresh tap water. But in the case of nitrates there is one nuance. Tap water already contains some amount nitrates, and if there are many of them, then this method may not work.

Use of special fillers for the filter.

Now, in modern aquarium filters, fillers are already provided for all occasions, and in the case of high nitrates, including. These are either specially soaked sponges, for example, Juwel Nitrax. Or fillers in the form of granules, such as Seachem De *nitrate, or API NITRA-ZORB. Maybe they will not lead to an instant effect, but in the future they will keep nitrates at a low level stably and for a long time.

Use of special chemicals for the aquarium.

Almost every manufacturer of aquarium products, in the presence of a special additive that can instantly reduce the level of nitrates in the water. For example, Tetra Nitrateminus, or Sera Toxivec. The latter not only lowers nitrates in the aquarium, but also removes ammonia, nitrites, chlorine, as well as heavy metals. I believe that you should always have it at hand, in case of unforeseen situations in the aquarium.

The popular method, using vodka.

If you do not go into scientific terms, the essence of this method is that vodka in the aquarium provokes the rapid growth of beneficial bacteria that remove nitrates from the aquarium. But this method is more suitable for saltwater aquariums. And it is necessary to strictly calculate dosages that are safe for fish and at the same time effective for lowering nitrates. Therefore, it is better to leave this method to professionals. And why use it if water conditioners are more efficient and much safer for the inhabitants of your aquarium.


Nitrates are not as deadly as ammonia or nitrites. But their excess can cause troubles such as weakened immunity in fish and the uncontrolled growth of algae in the aquarium. And since they are at the end of the nitrogen cycle chain, a decrease in the first two is likely to lead to a decrease in nitrates. In other words, do regular tests and keep an eye on the chemical balance in the aquarium.

Related articles:

Balance in aquarium!

Ammonia in aquarium!

Nitrite in aquarium!

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  1. my webpage says:

    Hello.This post was extremely interesting, particularly because I was looking for thoughts on this topic last Thursday.

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