Ammonia Not Converting to Nitrite [4 Main Reasons & Solution]

Ammonia converting to nitrite is a vital process in nitrogen cycling.

However, if ammonia is not converting to nitrite, it may signify an issue in the nitrification process, potentially caused by inadequate bacteria or high ammonia levels. This conversion is primarily carried out by beneficial bacteria known as Nitrosomonas.

Understanding the process of ammonia converting to nitrite is crucial for maintaining a balanced and healthy environment, especially in aquatic habitats such as fish tanks or ponds.

Testing water quality
Testing water quality is crucial

What Is The Process Of Ammonia Converting To Nitrite?

Ammonia converts into nitrite in a step by process. The absence of any of the steps will fail ammonia to convert into nitrite. Here is the breakdown of the process.

Colonization of Nitrosomonas bacteria: Nitrosomonas bacteria colonize surfaces such as gravel, filter media, or biofilm in the domain where ammonia is present. Bacteria need oxygen-rich environments to grow and thrive.

Sponge filter provides surface area for bacteria to colonize
Sponge filter provides surface area for bacteria to colonize

Ammonia uptake and oxidation: Nitrosomonas bacteria have unique enzymes, known as ammonia monooxygenases, which enable them to take up ammonia.

Once ammonia is absorbed by the bacteria, it undergoes oxidation, converting it into nitrite (NO2-). This oxidation process is crucial for breaking down toxic ammonia into a less harmful form.

Nitrification: The conversion of ammonia to nitrite is just the initial step in the nitrification process. Nitrite is further converted to nitrate (NO3-) by another group of bacteria called Nitrobacter.

Ammonia testing 2 PPM
Ammonia testing 2 PPM

Significance of nitrite levels: Nitrite is still toxic to aquatic organisms, especially fish, and high levels can lead to health problems.

The presence of nitrite indicates Notrosomonas bacteria colonization which is crucial for fish wellbeing.

Nitrite removal: Nitrite then converts into nitrates in the presence of Nitrobacter bacteria that convert nitrite to nitrate.

Nitrate, the end product of nitrification, can be utilized by plants as a nutrient source.

Why Might Ammonia Not Be Converting To Nitrite?

Ammonia is a crucial component in the nitrogen cycle of an aquarium, and it is supposed to convert into nitrite. However, there are several reasons why this conversion may not be happening effectively. Let’s explore some possible explanations:

New tank set up going through cycling Owner Christopher Ebenezer
New tank set up going through cycling Owner: Christopher Ebenezer
  • Insufficient beneficial bacteria: The conversion of ammonia to nitrite relies on the presence of beneficial bacteria, specifically Nitrosomonas. If the number of these bacteria is low or they are not actively growing, ammonia conversion may be hindered.
  • New tank syndrome: In newly established aquariums, the colony of beneficial bacteria might not be fully established yet. This can result in a delay in the conversion process, causing a buildup of ammonia.
  • High ammonia levels: Excessively high levels of ammonia can overwhelm the capacity of beneficial bacteria to convert it into nitrite. This can occur due to overfeeding, overstocking, or inadequate filtration.
  • Inadequate oxygen levels: Beneficial bacteria require sufficient oxygen to thrive and carry out ammonia conversion. In oxygen-deprived environments, such as poorly aerated tanks, the bacteria may be unable to function optimally, resulting in stalled conversion.
  • High pH levels: Ammonia conversion can be negatively impacted by high pH levels. In alkaline conditions, the activity of beneficial bacteria may decrease, leading to reduced ammonia conversion.
  • Toxic chemicals: The presence of certain chemicals or medications in aquarium water can inhibit the growth and activity of beneficial bacteria. This can interfere with the ammonia-to-nitrite conversion process.
  • Temperature extremes: Extreme temperature fluctuations, either too high or too low, can negatively affect the growth and activity of beneficial bacteria, consequently affecting ammonia conversion.
  • Improper maintenance: Neglecting regular aquarium maintenance, such as water changes and filter cleanings, can lead to a decline in the efficiency of the biological filtration system. This can contribute to poor ammonia conversion.

Among a lot of reasons, I’ll discuss in detail four major causes. Head over to the next section.

Reason #1: Presence Of Chlorine And Chloramine In Aquarium Water

Chlorine and chloramine are commonly used disinfectants added to tap water to make it safe for human consumption. While they are beneficial for us, they are harmful to the delicate ecosystem of an aquarium and kill beneficial bacteria.

It is crucial to dechlorinate the water first before introducing it into the aquarium. Dechlorination can be achieved using various methods, including using dechlorinating agents or letting the water sit for 24 hours to allow chlorine to dissipate.

Aquarium water test kits are readily available and can help you determine if chlorine or chloramine is present in your water. (My Pick: API Freshwater Master Test Kit)

By addressing the presence of chlorine and chloramine in your aquarium water, you can eliminate potential barriers to the conversion of ammonia to nitrite.

A beautiful tank set up with heater, filter, floating plants owner Mady Becker
A beautiful tank set up with heater, filter, floating plants Owner:Mady Becker

Reason #2: Incorrect Water Parameters To Grow Beneficial Bacteria

One reason ammonia may not convert to nitrite is due to incorrect water parameters, hindering the growth of beneficial bacteria necessary for the conversion process.

Maintaining the right water parameters is crucial for the growth of beneficial bacteria in your aquarium.

  • Inadequate water temperature: The temperature of the water plays a significant role in the bacteria’s ability to thrive. If the temperature is too high or too low, it can slow down their growth and activity. The ideal temperature for bacteria is 75~80 °F. Use a reliable heater to maintain the temperature at that range. (My Pick: HiTauning Aquarium Heater)
  • Incorrect pH level: Beneficial bacteria prefer a specific pH range (6.8~8.2) to function optimally. If the pH in your aquarium is outside of this range, it can hinder the bacteria’s ability to convert ammonia to nitrite. Regularly test the pH of your water and make adjustments if necessary to ensure it remains within the ideal range.
Heaters and bubblers in my community tank
Heaters and bubblers in my community tank

Reason #3: Too High Or Too Low Level Of Ammonia In The Tank

Having the right balance of ammonia in your tank is crucial for the conversion to nitrite to occur effectively. If the ammonia level is too high or too low, it can impede the conversion process and disrupt the nitrogen cycle in your aquarium.

  • High ammonia level: A high concentration of ammonia is toxic to aquarium inhabitants. Beneficial bacteria colonies may not convert to high levels of ammonia in the tank. Ammonia above 2 ppm is harder to convert for bacteria. The ideal range is (0.5~2 ppm)
  • Low ammonia level: On the other hand, insufficient ammonia levels can also hinder nitrite production. Bacteria need to be fed ammonia, when in a tank there are too low levels of ammonia, bacteria won’t get anything to feed. Ultimately they can’t grow. It occurs especially for a new tank.
Testing water using water testing kit
Testing water using water testing kit

So, if you have a new tank try adding ammonia externally (either by fish food or liquid ammonia). If you use liquid ammonia each 4 drops will raise ammonia by 0.5 ppm.

Be patient, and add ammonia gradually. Quick changes will put stress on aquarium inhabitants. After adding 2 ppm of ammonia, if you found the level becomes zero (0) within 24 hours, then it indicates your new tank is cycled.

If the ammonia level is too high perform water changes, reduce feeding, and add ammonia remover. Please read this article to know 9 techniques for reducing ammonia.

Reason #4: Level Of Oxygen In The Tank

Insufficient aeration in the tank can lead to low oxygen levels. Proper oxygenation is essential for the nitrifying bacteria responsible for converting ammonia to nitrite to thrive.

Without enough oxygen, these bacteria struggle to perform their vital role in the nitrogen cycle.

  • Overstocking: Overstocking the tank with fish or other aquatic creatures can deplete the available oxygen in the water. The more organisms in the tank, the higher the demand for oxygen.
  • Lack of surface agitation or aeration can restrict the exchange of gases, thereby decreasing oxygen levels in the tank. A calm water surface limits the absorption of oxygen from the atmosphere, which is necessary for maintaining a healthy oxygen concentration in the aquarium water.
  • Poor water circulation can lead to localized areas with low oxygen levels. In stagnant regions of the tank, the nitrifying bacteria may not receive the required oxygen, hampering their ability to convert ammonia to nitrite effectively.
  • High water temperatures can reduce the oxygen-carrying capacity of the water, potentially impeding the conversion of ammonia to nitrite. Warmer water holds less dissolved oxygen, causing a decline in the available oxygen levels for the nitrifying bacteria.

Test the oxygen level, and check for the signs of low oxygen level in the tank. If you found oxygen levels are inadequate take steps to increase the oxygen level.

Use air pump to aerate the aquarium
Use air pump to aerate the aquarium

Steps To Take If Ammonia Is Not Converting To Nitrite? [Boost Nitrogen Cycle]

If you’re experiencing a problem with ammonia not converting to nitrite in your aquarium, don’t worry! There are several troubleshooting steps you can take to boost the nitrogen cycle and restore balance to your tank.

#1: Adjusts Water Water Parameters

  • Test the ammonia levels: Use a reliable test kit to measure ammonia levels in your aquarium water.
  • Assess ph levels: Ensure that the ph of your water falls between the appropriate range (usually 6.8 to 8.0) for optimum bacterial growth.
  • Monitor temperature: Confirm that the temperature of your aquarium is suitable for the nitrogen cycle process (generally between 75 to 80 degrees Fahrenheit).

#2: Increase Oxygenation

  • Enhance aeration: Utilize an air pump or bubbler to increase oxygen levels in your tank, as oxygen is required for bacterial growth.

#3: Evaluate Biological Filtration

#4: Limit Overfeeding

  • Reduce food quantity: Overfeeding can result in excessive ammonia levels. Feed your fish an appropriate amount of food that they can consume in a few minutes, removing any excess promptly.

#5: Perform Regular Water Changes

#6: Patience Is Key

  • Allow time for the nitrogen cycle to establish: It takes time for nitrifying bacteria populations to establish and for the nitrogen cycle to stabilize. Be patient and monitor the progress of the ammonia to nitrite conversion regularly.

#7: Seek Professional Guidance

  • Consult with an aquarium expert: If you have followed the troubleshooting steps and are still experiencing issues with ammonia conversion, seeking advice from an experienced aquarium professional or veterinarian may be beneficial.
New tank set up
New tank set up

How Long Does It Take For Ammonia To Convert Into Nitrite? [Conversion Timeline]

Ammonia typically takes around 2-6 weeks to convert into nitrite in an aquarium setup. Understanding the time it takes for this conversion to occur is essential for a fishkeeper.

So, let’s delve into the details of how long it generally takes for ammonia to convert into nitrite.

Phase 1: Initial Bacterial Growth (0-2 Weeks)

during the first two weeks of setting up a new tank or introducing fish, the ammonia levels will start to rise.

At this stage, the nitrosomonas bacteria are actively colonizing surfaces and beginning their work in breaking down ammonia into nitrite. However, the conversion rate may be relatively slow due to the small number of bacteria present.

Phase 2: Steady Conversion (2-6 Weeks)

As the bacterial population increases, the ammonia conversion becomes more efficient. From the second to the sixth week, the time it takes for ammonia to convert into nitrite tends to decrease.

However, it is normal to still detect some ammonia during this phase, as the bacterial population may not yet be able to fully handle the ammonia load.

Phase 3: Stable Nitrogen Cycle (6-8 Weeks and Onwards)

By the sixth to eighth week, the nitrogen cycle should be well-established. Ammonia conversion to nitrite should occur within a shorter timeframe.

Usually within 24 hours, and the levels of both ammonia and nitrite should measure close to zero in a properly cycled tank.

Just a 14 days old planted aquarium
Just a 14 days old planted aquarium

Frequently Asked Questions

Why Is My Ammonia Not Converting To Nitrite In My Aquarium?

The lack of nitrite conversion is due to insufficient beneficial bacteria or high ammonia levels. Ensure proper filtration and water quality, and consider adding bacteria supplements to establish a healthy nitrogen cycle.

Can High Levels Of Ammonia Harm Fish?

Yes, high levels of ammonia can be harmful to fish. Ammonia toxicity can lead to stress, respiratory problems, and even death in fish. It is important to maintain proper water parameters and establish a stable nitrogen cycle to prevent the accumulation of excessive ammonia in the aquarium.

How Can I Reduce Ammonia Levels In My Aquarium?

To reduce ammonia levels in your aquarium, perform regular water changes to dilute the ammonia concentration. Ensure proper filtration and consider adding a chemical ammonia remover if necessary. Avoid overfeeding your fish and monitor the nitrogen cycle to prevent spikes in ammonia levels.


It is crucial to understand why ammonia might not be converting to nitrite in your aquarium.

Sometimes, the conversion process may not occur as efficiently as desired, leading to elevated ammonia levels and potential harm to your fish.

To address this issue, it is important to ensure that your aquarium has a properly functioning biological filtration system, which consists of beneficial bacteria that convert ammonia to nitrite.

Regular water testing and maintenance can help identify any imbalances and allow for appropriate adjustments. Additionally, avoiding overfeeding and properly cycling a new aquarium can help establish a stable nitrogen cycle.

Sujit Modak

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