The Nitrogen Cycle: The Key To Biological Filtration In An Aquarium

2023 Author: Molly Page | [email protected]. Last modified: 2023-11-27 22:49

Getting it right is the path to maintaining a healthy aquarium. The nitrogen cycle is responsible for biological filtration of the entire system. It prevents water from being polluted, removes organic pollution, waste and more … By understanding all this, we can prevent many problems in the future.

What is the nitrogen cycle?

In the nitrogen cycle, waste products of fish, plants and other organic pollution are decomposed by bacteria and fungi, releasing ammonia. Ammonia is extremely toxic to all aquarium inhabitants. Ammonia is released by the oxygen-loving bacteria Nitrosomonas. These bacteria feed on both oxygen and ammonia, and their waste product is a chemical known as nitrite. Although nitrite is not as toxic as ammonia, even a small amount of it in water is undesirable. Another type of bacteria, Nitrobacter, which also breathes oxygen, decomposes nitrite into harmless nitrates. Bacteria that feed on nitrates are called anaerobic, which means the following, they practically do not need oxygen for normal life. They already decompose nitrates into ordinary nitrogen.

Goldfish

Recent studies have shown that several other bacterial species (so far not named) are involved in the nitrogen cycle.

The nitrogen cycle in new aquariums

The new aquarium is in dire need of colonies of beneficial bacteria that carry out biological filtration. Therefore, a "cycle" must be started. This concept includes the process of establishing and maturing biological filters. To properly install the system, we must provide a source of ammonia so that the Nitrosomonas bacteria can multiply and colonize the system. In order to provide the aquarium with ammonia, it is better to plant there a couple of fish that are resistant to the presence of ammonia and nitrites in the water. However, some stores sell "live bacteria" to help keep your aquarium going. When buying hardy fish, ask for some gravel from the aquarium where it was previously kept. The gravel will be populated with bacteria, which will speed up the process. As soon as the fish enter the aquarium, they begin to feed and settle down, thereby producing ammonia. The Nitrosomonas bacteria will start to absorb this ammonia and populate the aquarium. Their greatest content will be found near filtration systems near the surface, where the most oxygen is. Since their number is limited and bacteria are not able to process all ammonia, their colonies will grow.

Fluctuations in the active response in aquariums

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As we can see, the fate of nitrites is somewhat simpler than that of ammonia. Nitrite is formed by the absorption of ammonia by the bacteria Nitrosomonas. The more bacteria, the more their metabolic products, that is, nitrites. Nitrobacter bacteria feed on nitrites, and therefore their colonies will also grow, following the colonies of Nitrosomonas. Nitrite levels will rise until the Nitrobacter population grows large enough to absorb nitrite faster than it will form. Thus, a balance will be established in the bacterial populations.

The end product of all of the above is nitrates. At low concentrations, nitrates are not harmful to plants or fish. On the other hand, nitrates can be excellent plant food, which can lead to trouble with algae. At the same time, anaerobic bacteria will degrade nitrates. Plants will also consume nitrates, which is a good natural way to control levels of this chemical. On the other hand, the nitrate level can be lowered with water changes and special chemicals.

Glass catfish

The time it takes to get your aquarium up and running depends on many factors. Such as the ammonia content in water, the presence of living rocks and many others. On average, this process takes 3 to 6 weeks.

The nitrogen cycle in neglected aquariums

A running aquarium is an aquarium where the biological filtration system has already matured and is working. There are also situations when the nitrogen cycle is disrupted in neglected aquariums. Such as; the use of medications, overfeeding of fish, or the introduction of new inhabitants.

Planting fish

The biofilter of a neglected aquarium has enough bacteria to deal with ammonia and dirt. When we add new fish, the load on the filter increases. How much toxin levels rise depends on how many inhabitants are added to the tank. If you add too many fish, the level of toxins can reach dangerous levels and lead to the death of the inhabitants of the aquarium. It is important to avoid these values by adding fish gradually to minimize the risk.

Such situations can arise in the following cases:

- If you buy fish through the mail. Due to the high shipping costs, many aquarists order multiple fish at once, putting them in the aquarium and thus jeopardizing the entire system.

- Settling several aggressive fish at the same time. It is better to give the fish time to acclimatize normally, then they will behave calmly and there will be no battles for the territory.

- Quarantine fish. A jig aquarium is most often a small tank with minimal filtration. The level of toxins should be carefully controlled by adding any number of fish there.

Discus, photo photography underwater world pixabay

Turquoise discus

- Unnoticed death. In many freshwater aquariums and reef systems, an inhabitant may die in a shelter and be difficult to spot. In this case, the body will begin to decompose, putting a heavy load on the biofiltration system. A large aquarium is more convenient in this case. This is how ammonia released by a dead body will be dissolved in a large amount of water.

- Overfeeding. When feeding, keep in mind that the food you are serving must be eaten within 3-5 minutes. After a few hours, any nutrients will be decomposed by bacteria and fungi, releasing ammonia into the water. It is this ammonia that can overload the biological filtration system and lead to malfunctions in the entire aquarium system. If the aquarium is still overfed, remove the food from the water and change the water 25% of the volume of the aquarium.

- Use of medicines. Many medications affect the ability of bacteria to function properly in biofilters. Antibiotics, for example, kill many types of beneficial bacteria. Unfortunately, biological filtration is bacteria-based and will be disturbed by any treatment. It is important to constantly monitor the aquarium and make timely water changes and apply chemicals on time.

Related article Protecting your aquarium from toxins

- System maintenance. Water changes and maintenance of filtration systems will affect the biological filtration system to some extent. When changing the water, it is important that the water is pre-purified of chemicals such as chlorine. Chlorine can kill beneficial bacteria, so water conditioners should be used to get rid of the chemicals in the water. Improper filter maintenance can also lead to trouble. The beneficial bacteria responsible for the nitrogen cycle are usually found in areas with the highest oxygen content, i.e. filters. When servicing filters, ideally leave the biological filtration systems alone and do not touch them.

Restoring balance

All of the above can lead to interruptions in the nitrogen cycle. It is important to always monitor changes in water quality. If the level of ammonia or toxins is increased, it is necessary to bring it back to normal by changing the water or using special preparations. When carrying out a water change, it is important to know that more than 25% of the total volume of the aquarium cannot be changed. Otherwise, pH and temperature problems can arise, leading to stressful situations for the fish. Therefore, if toxins are present in the water, it is best to carry out minor but frequent (perhaps even daily) water changes to avoid major changes. There are many products commercially available to control ammonia levels.