The nitrogen cycle - the heart of your aquarium!!!

1. Introduction

Cycling an aquarium is one of the most important and sometimes underestimated steps in the setup of a healthy aquatic environment. This process is essential to create a balanced ecosystem, where organic waste, such as excrement and food debris, is converted into less toxic substances through a biological process known as nitrogen cycle.

Without proper cycling, the accumulation of ammonia and nitrites, highly toxic substances for fish, can cause severe stress, diseases and even the death of aquatic inhabitants. During cycling, a stable colony of beneficial bacteria develops, which play a vital role in biofiltration, converting these toxins into nitrates, which are much less harmful.

While the process may seem time-consuming or technical, there are several strategies and products that can speed it up, allowing the aquarium to quickly reach a state of biological maturity. This article explores best practices, quick solutions and how to ensure success in preparing your aquarium for your aquatic inhabitants.

2. What is the cycling of an aquarium?

The cycling of an aquarium is the process of establishing a biological balance in the aquatic system. In simple terms, it creates an environment in which the waste produced by fish and other organisms does not result in toxic conditions.

2.1. importance of cycling

Without cycling, organic residues (feces, food scraps and decomposing plants) accumulate rapidly, generating ammonia. This compound is extremely toxic to fish, even at low concentrations. Without beneficial bacteria to process ammonia, the environment becomes unsustainable.

2.2. Cycling steps

1. Ammonia increase:
   Initially, ammonia is generated from organic waste or the addition of ammonia sources.
   
2. nitrites formation:
3. Over time, bacteria of the genus nitrosomonas begin to convert ammonia to nitrites. Nitrites are less toxic than ammonia but still pose a danger to fauna.
4. Conversion to nitrates:
   Finally, the nitrobacter turn nitrites into nitrates. These are relatively safe even at levels that we consider high for an aquarium (>50ppm) and can be controlled with partial water exchange.

Cycling usually takes 4 to 6 weeks, but it can vary depending on aquarium conditions and methods employed. can be more or less time consuming.

3. The nitrogen cycle in the aquarium

3.1. How nitrogen impacts the aquarium

Nitrogen is essential for life, but its form and concentration determine whether it is beneficial or harmful. Ammonia and nitrites are deadly for fish, while nitrates, when in excess, encourage the growth of algae, causing aesthetic and biological imbalances. But they have a very low toxicity for fish, even at high values.

3.2. Beneficial Bacteria: The Healthy Aquarium Pillar

Beneficial bacteria are not visible to the naked eye, but play an essential role in the health of the aquarium.

3.1 Nitrifying bacteria: responsible for the nitrogen cycle.

nitrosomonas

1. Function:
   • Oxidize ammonia (NH3) in nitrites (NO2⁻), the first step of the nitrification cycle.
2. Metabolism:
   • They are chemoautotrophic, that is, they obtain energy by the oxidation of inorganic compounds (ammonia).
   • They fix carbon dioxide as a carbon source for their growth.
3. Ideal environment:
   • pH: They prefer pH between 7.5 and 8.5.
   • Temperature: Optimal activity between 20°C and 30°C.
   • Oxygenation: They need high levels of oxygen for their aerobic metabolism, so there should be good agitation on the surface of the water to ensure good gas exchange and keep the water well oxygenated.
4. growth:
   • They grow slowly, taking several days to form meaningful colonies, this taking the ideal conditions, not having the process is even slower.
5. Sensitivity:
   • Sensitive to sudden changes in pH, extreme temperatures and chemicals such as chlorine and medicines, so in our aquarium we should never add tap water without leaving it at rest or without adding an antichlorine conditioner, as well as, we should never wash the filter with direct tap water.

nitrobacter

1. Function:
   • nitrites oxidize (NO2⁻) in nitrates (NO3⁻), the second step of nitrification.
2. Metabolism:
   • Like nitrosomonas, they are chemoautotrophic.
   • The energy generated is used to fix carbon dioxide.
3. Ideal environment:
   • pH: They grow best in slightly alkaline pH, but can tolerate up to 6.5.
   • Temperature: Optimal activity also between 20°C and 30°C.
   • Oxygenation: They depend on oxygen, but are less sensitive to their reduction than nitrosomonas.
4. growth:
   • They also have slow growth, but follow the nitrosomonas as nitrites accumulate.
5. Resistance:
   • They are a little more resistant than nitrosomonas to adverse environmental conditions.

3.2 Denitrifying bacteria: 

They play an important role in the nitrogen cycle, by converting nitrates (NO3⁻) into forms of gaseous nitrogen (N2 or nitrous oxide, N2O), which are released into the atmosphere. This process, called denitrification, is crucial to close the cycle nitrogen in aquatic and terrestrial systems, reducing the levels of nitrates accumulated in the water.

Characteristics of denitrifying bacteria

1. 1. Function:
      
      • convert nitrates (NO3⁻) into gaseous nitrogen (N2) or nitrous oxide (N2O).
      • This process occurs in conditions of low oxygen availability, as they are anaerobic bacteria.
   2. Genre examples:
      
      • pseudomonas
      • paracoccus
      • bacillus
      • alkaligenes
   3. Metabolism:
      
      • They are heterotrophic, using organic carbon as an energy source.
      • Denitrification is an alternative respiratory process, where nitrates and nitrites serve as final electron acceptors instead of oxygen.
   4. Ideal environment:
      
      • Anaerobic conditions: They grow in environments where dissolved oxygen is low or non-existent, such as deep zones of saturated substrates or biological filters.
      • organic carbon: They need an organic carbon source (such as acetate, ethanol or natural organic matter) for their metabolism.
      • Ph: Prefer neutral to slightly alkaline pH.
      • Temperature: They develop well at temperatures between 20°C and 35°C.
   5. Sensitivity:
      
      • inhibited by the presence of high levels of dissolved oxygen.
      • depend on adequate sources of carbon and nutrients to thrive

It may seem that it is essential to have many of these bacteria, but keeping a well-oxygenated aquarium they are confined to the bottom of the substrate and if there is little water circulation in the filter. The denitrifying function may or may not be useful, seen in the case of the planted ones with the plants as consumers of nitrates, in this case the denitrifying bacteria will compete for the nitrates with the plants.

3.3. where bacteria develop

They inhabit porous and rough surfaces, including:

• filter sponges
• substrates
• decorations
• Internal glass surfaces

3.4. How to maintain and stimulate beneficial bacteria

• Avoid excessive cleaning: Washing in chlorinated water kills the bacteria. Too frequent washes eliminate a significant part of the bacterial flora that we want to preserve. I would say that in the case of an external filter, the cleaning should be performed when we notice less flow of output at the water outlet.
  If you feel the need to clean the filter weekly or monthly, most likely your filter is not suitable or is poorly configured for your aquarium.
• Avoid excess chemicals: Medications can be harmful to bacterial colonies, such as the use of antibiotics or other antibacterial medications for fish.
• Ensure good oxygenation: Oxygen is essential for nitrifying bacteria, we must therefore ensure a good circulation of water throughout the aquarium and a ripple on the surface of the water that guarantees a good gas exchange between the water and the air. Air pumps can help with water oxygenation, but they may prove to be counterproductive in a planted aquarium, especially with CO2 injection.
• Good average quality: These bacteria need adequate surfaces to grow, such as filter media, substrates and plants. Of course, the substrates, plants and other objects in the aquarium do not provide enough surface area for the bacterial colony we want, to have this area of enormous surface we need biological media that are nothing more than materials than because of their physical characteristics they have a very porous structure that creates a very porous structure that creates Space for bacteria to live and that in addition allow the circulation of water throughout the element so that the water rich in oxygen reaches everywhere. Therefore, a ideal biological media has a very large surface area given its size and allows a circulation of water throughout its structure.

3.3. The role of ammonia, nitrite and nitrate

• Ammonia (NH3): Extremely toxic, especially at high pH, in NH3, in more acidic media it is found as much less toxic NH4.
• nitrite (NO2): Less toxic than ammonia, but interferes with the fish's ability to carry oxygen in the blood, which can cause difficulty in breathing and hypoxia.
• nitrate (NO3): Usually safe at levels below 40 ppm, but according to various studies nitrate tolerance can go above 100ppm without damage.

4. How to inoculate the aquarium for cycling

Inoculating the aquarium means introducing beneficial bacteria at first to speed up the cycling process. In this way we can shorten the time it takes to complete the nitrogen cycle.

4.1. Natural methods of inoculation

4.1.1. Filter Media Transfer:
Using media from filters from an already cycled aquarium is an efficient method of introducing bacteria. This is the fastest method of being able to complete cycling, since in the new aquarium there is enough food for the survival and multiplication of the various species of bacteria.

True, it is perfectly possible, in this case we can always ask a friend or acquaintance with an already established aquarium to make this donation, if you don't know anyone, you can always ask in a whatsapp or Facebook group, if anyone close to you can make this donation, it will not harm the donor's aquarium.

4.1.2. Use of mature substrate:
Adding sand or gravel from a stabilized aquarium can contribute significantly. Although it contains less bacteria than the media remains a good source.

4.1.3. Add fish moderately:
Introducing one or two resistant fish to generate waste and stimulate the growth of bacteria is a common practice, but it must be done with great care so as not to sacrifice any fish and this one would say that is the method I least recommend.

4.1.4. Add a small portion of land: It may seem strange to add earth to our aquarium, the truth is that the soil is very rich in nitrifying bacteria, soil from a planted vase, a garden, somewhere that is using it, should not be earth/soil "virgin". It estimates that only one gram of land contains about 19 million beneficial bacteria, which will be a great start for an aquarium. The earth portion can be confined to a cotton fabric or a closed glass sock and placed next to the intake of the filter for the bacteria to migrate and lodge in the filter.

4.2. commercial products to speed up the process

There are several products available that contain live bacterial cultures, however we must always think that just adding bacteria will not be enough if they do not have ammonia, nitrites and other essential nutrients for them.

5. Mature Aquarium: What does it mean?

A mature aquarium is one that has already gone through the initial cycling phase and has reached a stable biological equilibrium state. Although the nitrogon cycle continues to occur constantly, the system as a whole becomes more resilient to fluctuations, population growth, excess food, decomposing plants, etc.

5.1. Difference between cycled and mature aquarium

• Cycle Aquarium: A newly established aquarium, where nitrifying bacteria are already active, but colonies can still be unstable. This aquarium continues in a fragile balance and problems can occur in the event of sudden changes in temperature, pH, introduction of fish or simply overfeeding the inhabitants of the aquarium. 
• mature aquarium: An older system, where bacteria, microorganisms and even plants form a well-balanced ecosystem. This aquarium is resistant to oscillations, the water is crystal clear and healthy, ensuring the best health of the fish and the absence of disease.

A mature aquarium is less susceptible to ammonia spikes or nitrites, as the bacteria have already settled completely on all available surfaces.

5.2. Benefits of a mature aquarium

• Chemical stability: ammonia levels and nitrites close to zero consistently.
• Lower maintenance: The biological filter already plays its role effectively, reducing the need for frequent interventions.
• Best fish health: Less stress caused by fluctuations in water parameters.

6. Biofiltration: the heart of the nitrogen cycle

6.1. How does biofiltration work?

This is the most important component of the aquarium filtration system.

• First step: The mechanical filter retains larger particles, such as food scraps, waste, and plant rest.
• Second stage: Biofiltration comes into play, where nitrifying bacteria convert ammonia into nitrites and, later, into nitrates.

6.2. Types of biological filters

1. Sponge filters:
   Simple, economical and effective, especially for smaller aquariums. The sponge serves as a surface for bacteria to develop, contrary to what many aquariumists think, sponges are great biological media and have a vast surface area where bacteria can live depending on their PPI. However, these filters given their small size, have a low filtration capacity and are recommended only for very small and poorly populated aquariums.
2. External canister filters:
   Ideal for larger aquariums, they offer great biological media capacity. These filters are also easy to customize with different types of media. They are the best solution for medium to large aquariums, with a reservoir with several liters of capacity, we can fill them with media to house all the bacterial flora, without "home" for the bacteria they will not develop enough to create a large bacterial flora and stable. 
   Sometimes we focus on the flow capacity of a filter, in L/H, but I would say that more important is the size of the "bucket", I prefer a filter with 800LH and with a bucket of %L of capacity, than an internal sponge filter connected to a 1500LH water pump.
   
   
3. Sump filters:
   Widely used in marine systems or large aquariums, sumps are additional tanks that allow for more robust and versatile filtration, once again due to their capacity in liters to place various biological media, certain sumps can have 10, 20 or 30L or more of capacity, with various stages of filtration and a large amount of media being created.
   
4. Hang-on-back (HOB) filters:
   Small and practical, they are ideal for beginners and small to medium-sized aquariums. Although they do not have the disadvantage of the internal filters that take up space inside the aquarium, they most often end up being undersized in their ability to place media and often due to their positioning and outflow of water, it becomes difficult to optimize the circulation of water throughout the aquarium.

7. Debris in the aquarium: what they are and how to manage them

7.1. Explained Debris

Debris are organic and inorganic materials that accumulate in the aquarium, such as:

• fish feces.
• leftover food not consumed.
• decomposing plants.

Although some debris is unavoidable, excess can cause problems such as:

• ammonia increase.
• algae growth.
• Unpleasant appearance in the aquarium.

7.2. The role of the “Brown Gunk” in the filter

The "Brown Gunk" or "Brown Slope", which I named "Ouro Lamacento" in one of the videos I left on Facebook cleaning my filter is a biofilm that forms in the filter media and other surfaces inside the filter. This apparently dirty material is actually composed of beneficial bacteria and other microorganisms that help in the biofiltration process. This brown goo that we think is dirty is the soul of biological filtration and the secret of a healthy, balanced aquarium with crystal clear water.

• Benefits: essential for the nitrogen cycle.
• Careful cleaning: Never wash filter media with tap water, as chlorine can kill bacteria. Use the aquarium's own water.

The video of my filter cleaning after 6 or more months since the last cleaning:
https://www.facebook.com/Hydra...

7.3. Blurred water and its causes

Blurred water is a common problem in aquariums, especially in newly assembled systems. Some causes include:

1. Bacterial flowering: a temporary peak in the growth of suspended bacteria.
2. Overfeeding: Unconsumed food particles can float in the water.
3. Inefficient filtering: An inappropriate or dirty filter can leave particles suspended.

How to solve:

• Perform partial water changes.
• Adjust the amount of food provided.
• Check filter efficiency.

8. Cycling in planted aquariums

8.1. Benefits of natural plants in the nitrogen cycle

Natural plants are powerful allies in maintaining a healthy aquarium. They consume ammonia and nitrates as a source of nutrients, helping to stabilize chemical parameters. It can help control algae episodes and excess nutrients, however, plants when consuming ammonia are competing with bacteria for food.

• Natural filtration: The plants complement the work of the biological filter.
• Algae Reduction: By consuming nutrients, plants compete with algae, inhibiting their growth.

8.2. Cycling with plants versus without plants

This could be a somewhat controversial topic, I almost always advise you to completely plant the aquarium with all the plants we want to have from the beginning of cycling, however, when the objective is to do the cycling as soon as possible I would say . . . The best thing is to do the cycling without plants!!!

"So why do you say you recommend planting everything from the beginning???"
Simple, because my clients are focused on having an aquarium planted and not cycling as quickly as possible.
In this case, it pays to plant right at the beginning, even if it can compromise the speed of cycling, the plants, from the beginning, adapt to the aquarium, they take root and become stronger and metabolically more active so they can consume all the excess nutrients released by the Substrate and nitrates, which will also be produced as the final product of the nitrogen cycle, thus creating a faster balance and can also inhibit algae.
but . . . 
               . . . In fact, the plants in the aquarium since the beginning of cycling will compete for food with the bacteria, because the plants will absorb the ammonia that the bacteria also need to feed and multiply from the water, and this can delay cycling, and let's be Sincere, few will be the aquariums who will want to have a "stop" aquarium and without light for 3/4 weeks without being able to appreciate it.

the facts

The fastest cycling possible It is made by inoculating the aquarium with beneficial bacteria, for example from another aquarium as we saw above, another factor is to feed the bacteria, I can add fish food to the aquarium to produce ammonia or I can add a commercial product that contains all the nutrients that the nitrosomonas and nitrobacter They need to grow and multiply fast, which is not just ammonia and nitrites, they need several other nutrients in their biology, If only there were any of these products on the market. . .
We can think that having high levels of ammonia in the aquarium is absurd when we fight so that there is no trace of this ammonia in the aquarium given the toxicity to the fish, but remember we are in the cycling, there will be no fish in the aquarium, the Ammonia can perfectly be at 50ppm and nitrites equal There is no risk, except to make the cycling faster.

"But everyone knows that high ammonia levels cause immense algae and is a common cause for it"
true, but for there to be algae there must be light, but to do the cycling there is no need to have 5/6 hours of light, in fact it does not need light at all, the nitrifying bacteria do not perform photosynthesis, so the light can be off during cycling, since we are also cycling without plants. 

"So how can I make cycling faster and more effectively?"
I can cycling without plants, without light, inoculating and feeding the bacteria in this way. End the cycle in 10-12 days Instead of 40 to 50 days (this is the time it takes, even, to finish the cycling) and I have the cycled aquarium and ready to receive all the plants and I can even add fish, and not just 2 or 3, because this cycling provides a colony Already well sized, it is a very valid and fast option and easily contour the problem of algae during cycling. hmmm what do you think of the idea???

"How do I know the cycling is complete?"
When performing a test and the ammonia and nitrites values are at 0ppm and the nitrates must be high, be aware that the tape tests are not as reliable as those of droplets, if there is no ammonia but there is nitrites, the cycle will be halfway through, we already have nitrosomonas but the nitrobacter are missing.

Having low results in ammonia and nitrites can mean that the aquarium does not have enough "food" for the bacteria, more than having the cycle to finish, if there is never too much ammonia in the aquarium, it is normal for the tests to give a low value or even zero at the beginning.
We can extrapolate that, in order to have the cycle finished and an already effective bacterial flora, the ammonia reached 0ppm as well as the nitrites, but the nitrates are very high, this is a sign that the filter already has the ability to convert a large amount of ammonia and nitrites.

Attention: It can happen in the tests, do not accuse ammonia or nitrites, and that does not mean complete cycling, but rather it has not even started. If you never add ammonia or sources of ammonia to the aquarium, you can test the aquarium after 5 days of operation and be at zero.

9. Conclusion

Establishing and maintaining a healthy aquarium is not an immediate process, but with patience and dedication, anyone can create a balanced and lasting ecosystem. The understanding of cycling, the nitrogen cycle and biofiltration are the foundations for success. By following appropriate practices such as bacteria inoculation, use of natural plants and careful maintenance of the filter, it ensures a safe and favorable environment for your fish and plants.

Consider the nitrogen cycle and its bacterial flora as the heart of the aquarium, it is the key to the success of the aquarium, from the health of the fish, the appearance of algae, crystalline water, safe water parameters, etc.

Remember: each aquarium is unique and, over time, the aquariumist will develop a deeper understanding of the specific needs of your system and be able to diagnose when something is wrong.

briefly. . . 

"Procedure for a cycling in record time (and soon with a very effective bacterial flora)"

* Front image source:https://www.animates.co.nz