This post may contain affiliate links. By using these links, you support AquariumForce. We may receive a commission for any purchases made through these links, at no additional cost to you. Read more.

The Expert Guide to Reducing Ammonia in Your Aquarium

Aquarium hobbyists must keep a close eye on ammonia levels as it’s a critical parameter for the health and happiness of their fish. This nitrogenous compound can quickly become deadly if left uncontrolled.

However, managing aquarium ammonia levels is easier than you might think. In this article, we’ll explore all the essential steps to help you create a safe and stable environment for your aquatic pets. So let’s dive in!

What is Ammonia and Why is it Important?

Ammonia is a compound composed of nitrogen and hydrogen, with a chemical formula of NH₃. It’s a colorless gas that readily dissolves in water.

Ammonia is commonly used in household cleaners and in agriculture as a fertilizer. However, in an aquarium, it can contaminate the water and become toxic to fish and other aquatic life.

To maintain a healthy fish tank, it’s important to maintain ammonia levels at 0.0 PPM (parts per million) through establishing biological filtration that handles ammonia, such as the nitrogen cycle, and having strategies in place to manage sudden increases in ammonia levels, such as water changes and adding beneficial bacteria.

It’s crucial for all fishkeepers to be aware of the dangers associated with ammonia and how to test and effectively control its presence.

Test Solutions for Ammonia, Nitrite and Nitrates

Sources of Ammonia in Aquariums

Ammonia in aquariums primarily comes from fish waste containing protein and from the decomposition of organic matter such as rotting food and dead plants (1).

However, there are other sources of ammonia in the aquarium, such as:

  • Tap water (depending on your water source).
  • Medications used to treat fish diseases.
  • Certain types of substrate, such as sand or gravel.
  • Aquarium decorations, such as rocks or driftwood that have not been cleaned properly.

Overview of the Nitrogen Cycle in Aquariums

Before introducing fish to your aquarium, it’s important to establish the nitrogen cycle, which is essential for a healthy aquarium.

The nitrogen cycle addresses the presence of ammonia in your aquatic ecosystem. Initially, ammonia is generated from fish waste and rotting food.

Thankfully, Nitrosomonas, a nitrifying bacteria, comes into play and consumes ammonia, effectively keeping its levels at 0 PPM if there is enough of it in the tank.

As a byproduct, Nitrosomonas produces nitrites (NO2−), which are also harmful to fish. However, Nitrobacter, another nitrifying bacteria, consumes nitrites, ensuring their levels stay at 0 PPM.

Lastly, Nitrobacter produces nitrates (NO3-) as waste. Nitrates are not harmful to fish if they are below 20 PPM, but it’s recommended to manage them by conducting a water change once they reach 10 PPM.

Although a healthy fish tank can be a low-maintenance environment due to the natural processes like the nitrogen cycle that control the chemical balance, it’s important to remember that ammonia still needs to be monitored even after the tank is cycled.

What is the Safest Ammonia Level for Fish in Aquariums?

The safest level of ammonia for fish in both freshwater and saltwater aquariums is 0 PPM. Even a reading of 0.25 PPM of ammonia is considered harmful to fish and requires immediate action to be taken.

Dangers of High Ammonia Levels in Aquariums

Ammonia is highly toxic to both freshwater and saltwater fish, causing harm even at low concentrations. It can burn the gills, increase stress levels, and weaken the immune system, making the fish more susceptible to diseases.

As ammonia concentration increases, it becomes difficult for fish to excrete the waste, which can lead to damage to internal organs, blood, and tissues (2). The accumulation of ammonia in the brain can cause ammonia neurotoxicity, leading to damage to the nervous system and brain function. Ultimately, high ammonia levels can prove fatal for fish.

Symptoms of Ammonia Poisoning in Fish

Fish will display various symptoms when aquarium ammonia levels are high. Let’s take a look at some common signs of ammonia poisoning in fish.

  • Gasping for air: High levels of ammonia can increase the respiration rate of fish, causing them to gasp for air at the water’s surface.
  • Red or purple gills: Ammonia enters the fish’s body through the gills, causing irritation, bleeding, and discoloration of the gills.
  • Burns or lesions on the body: Concentrated ammonia can cause burns on the scales, particularly in sensitive areas like the fins, tail, and gills.
  • Weak immune system: Ammonia poisoning can weaken the fish’s immune system, making them more susceptible to bacterial and parasitic infections.

Some common early signs of ammonia poisoning in fish include a lack of appetite, lethargy, stress behavior such as hiding, and fish lying at the bottom of the tank.

Effects of High Ammonia Levels on Aquarium Plants

Plants are capable of absorbing ammonia from both air and water and converting it into nitrogen, which is a source of nutrition for them (3, 4). However, high levels of ammonia can damage plant leaves, reduce growth, and even kill the plants. This is because plants rely on a balance of nutrients and chemical compounds in the water to survive, and excessive ammonia can throw this balance out of whack.

When ammonia levels are high, plants may display signs of stress such as yellowing leaves, stunted growth, and wilted or rotting stems. Additionally, high ammonia levels can lead to an overgrowth of algae, which can also negatively impact plant growth and health.

Test for Aquarium Ammonia Levels

Common methods to test for ammonia in your tank include liquid tests and paper strips. Additionally, electronic meters, ammonia test kits, aquarium controllers, and laboratory testing are also available options to measure ammonia levels in your aquarium.

Liquid Tests

Liquid tests are easy to use and provide highly accurate results. They can identify ammonia levels in increments starting from 0 PPM, with the next levels being 0.25 PPM to 4 PPM, and beyond.

To perform a liquid test for ammonia, simply collect a sample of aquarium water in a test tube and add a few drops of test solution following the manufacturer’s instructions.

The test solution will cause a color change in the aquarium water, indicating the presence of ammonia, and you can refer to the provided color chart to determine the result. Typically, a bright yellow color on the chart indicates an ammonia concentration of 0 parts per million (PPM), which is the desired result.

If you have a freshwater aquarium, it’s recommended to use the API Freshwater Master Test Kit. This kit includes tests for all the major water parameters such as nitrite, nitrate, pH including ammonia. For saltwater aquariums, you can use the API Saltwater Master Test Kit. Both of these test kits are reliable and easy to use.

API Freshwater Master Liquid Test Kit

Paper Strips

Paper strips are an alternative method to test for ammonia in your aquarium. They are simple to use – you just need to dip the test strip into your aquarium water and compare the color change on the strip to the provided chart.

However, it’s important to note that test strips are generally less accurate and expensive than liquid tests. Since ammonia levels can greatly impact the health of your fish, and even a small difference (0.2 PPM) in ammonia concentration can be critical, it’s highly recommended to use liquid tests over test strips for more reliable results.

Paper Test Strips

Best Practices for Accurate Ammonia Testing

Accurate and reliable testing of ammonia levels is crucial for maintaining a healthy aquarium. Follow these tips to ensure that you get accurate results:

  • Test your aquarium water for ammonia, pH, nitrate, and nitrite levels on a weekly basis to monitor changes over time.
  • Use liquid tests for ammonia instead of test strips since they are more accurate.
  • Wait for 5 minutes before comparing the color of the solution to the chart when using liquid tests.
  • Always use an up-to-date color chart provided by the manufacturer to ensure accurate results.

Remember, misreading the results could have severe consequences for the health of your aquarium inhabitants. So, accuracy is key when testing for ammonia levels in your aquarium.

Causes of High Ammonia Levels in the Aquarium

To keep your aquarium’s ammonia levels at a safe and stable level, it’s essential to understand the potential causes of ammonia spikes. Here are some common causes of high ammonia levels in aquariums:

  • Overstocked aquarium: Too many fish in the aquarium can produce more waste than the nitrifying bacteria can process, leading to an increase in ammonia levels. Consider reducing the number of fish or increasing the size of the aquarium.
  • Overfeeding: Uneaten food decaying in the substrate can release ammonia, creating an unnatural source of ammonia and causing a spike in levels. Be sure to feed your fish only the amount they can consume in a few minutes.
  • Filter malfunction: If the filtration system is not functioning properly, it can result in an increase in ammonia levels. Dirty filter pads can also contribute to an ammonia spike. Clean or replace filters regularly.
  • Dead plants and rotting algae: Decaying plants and algae in your tank can release ammonia, which can cause an increase in levels. Even healthy plants can release ammonia if leaves and branches break off and decay. Remove dead or decaying plant matter promptly.
  • Lack of nitrifying bacteria: Nitrifying bacteria play a crucial role in the nitrogen cycle. Accidentally removing them during tank cleaning can result in an ammonia spike. Avoid excessive tank cleaning or disturbing the substrate unnecessarily.
  • Dead fish or crustacean: When an aquatic creature dies, its decaying body can cause an ammonia spike. It’s important to remove dead animals from the tank immediately to prevent an increase in ammonia levels.
  • Introducing ammonia in new water: Tap water treated with chloramine may contain ammonia. Adding untreated tap water during a water change can increase ammonia levels. Use a water conditioner that neutralizes chloramine before adding new water.
  • Lack of tank maintenance: Neglecting regular tank maintenance can lead to a build-up of rotting food, plant matter, and other factors, resulting in high ammonia levels. Perform regular water changes, clean the substrate, and remove debris and decaying matter promptly.

How to Reduce Ammonia Levels in Aquariums

If the nitrogen cycle is functioning properly, ammonia levels should remain at 0 PPM. However, there are instances when ammonia levels can spike, requiring appropriate action to reduce them effectively. Following are the ways to reduce ammonia levels in your aquarium.

Perform a Water Change

Performing a partial water change is an effective method to reduce ammonia levels in your aquarium. Ammonia is water-soluble, meaning that it dissolves in water, so removing some of the water and replacing it with clean, fresh water can lower the overall concentration of ammonia in the tank.

It’s important to test your source water for contaminants before adding it to your tank. Municipal water supplies may contain chloramines or other chemicals that can harm your fish, so you should use a water conditioner, such as SeaChem Prime, to neutralize these chemicals before adding the water to your tank.

If you want to ensure the complete purity of your source water, you can consider using a Reverse Osmosis (RO) filtration system. This system removes impurities from the water, including chlorine, chloramines, heavy metals, and other chemicals.

When performing a water change, it’s recommended to change about 25% to 50% of the water in your tank, depending on the ammonia concentration. If your aquarium has an ammonia concentration of 0.5 PPM or higher, a 50% water change is recommended to help reduce the ammonia levels effectively. Be sure to use a gravel vacuum to remove any waste or debris from the substrate while performing the water change.

Use Aquarium Filter To Lower Ammonia Levels

Aquarium filters play a crucial role in maintaining water quality and controlling ammonia levels. The filter helps by providing a surface for beneficial bacteria to grow and break down harmful substances like ammonia. These bacteria convert ammonia into less harmful nitrite and then into nitrate, which is removed from the water through regular water changes.

It’s important to choose the right filter for your aquarium size and stocking levels. A filter that is too small or not powerful enough won’t be able to handle the waste produced by your fish, leading to an increase in ammonia levels. In addition, dirty filter pads/sponges can contribute to ammonia spikes, so it’s crucial to clean or replace the filter media regularly.

While filtration can help lower ammonia levels, it may take longer than a water change to have an effect. If your ammonia levels are consistently high, you should consider using filtration in addition to regular water changes. However, for sudden ammonia spikes, a water change is the quickest and most effective way to reduce ammonia levels.

Add Water Conditioner

Water conditioners can be an effective way to remove ammonia from your aquarium without having to perform a water change. They can be effective for ammonia concentrations around 0.25 PPM.

Water conditioners work by neutralizing ammonia (NH3) and converting it into ammonium (NH₄⁺), which is less harmful to fish. However, it’s important to note that water conditioners don’t remove ammonia from the water, but rather convert it into a less toxic form that can be safely processed by nitrifying bacteria.

When choosing a water conditioner, it’s important to select one that’s designed specifically for removing ammonia. Some water conditioners may only be effective for removing chlorine or chloramine from tap water and may not help with ammonia removal.

It’s also crucial to follow the manufacturer’s instructions carefully to ensure the correct dosage for your aquarium size and ammonia concentration. Overdosing can cause harm to your fish and may lead to further ammonia spikes.

Remember that while water conditioners can be effective for slightly elevated ammonia levels, they may not work as quickly or effectively as a water change for more significant ammonia spikes.

Use A Cycled Aquarium Filter

Using a cycled filter from a previously established aquarium can introduce a healthy population of nitrifying bacteria to your new aquarium.

It’s important to note that the beneficial bacteria mainly reside in the filter media, so avoid replacing it entirely or cleaning it with tap water, as this can kill off the bacteria. Instead, rinse the filter media in aquarium water to remove any debris and maintain the bacterial population.

To assess the effectiveness of the new filter and determine whether further action is necessary, it’s essential to monitor the water quality regularly by testing it every 24 hours. This will help you determine whether the filter is producing the desired results and whether additional steps are required to reduce ammonia levels in your aquarium.

Temporarily Stop Feeding Your Fish

Feeding your fish is one of the primary sources of ammonia in your aquarium. Temporarily stopping feeding your fish can help reduce the amount of waste produced, which in turn can lower ammonia levels. However, it’s important to not starve your fish, as they still need to eat to stay healthy.

If you decide to fast your fish, it’s recommended to do so for no longer than three days. This will give the beneficial bacteria in your filter time to break down the ammonia produced by fish waste. During this time, you should also continue to monitor ammonia levels using a test kit to ensure they are decreasing.

It’s important to note that this method may not be effective for all situations, especially if your aquarium is heavily stocked.

Adjust Other Parameters of Your Tank

Ammonia toxicity is affected by other parameters in your tank, such as temperature and pH. Higher temperatures and alkaline pH levels increase the toxicity of ammonia, making it more harmful to your fish. Even a small change in pH or temperature can push the water beyond safe levels.

To reduce the harmful effects of ammonia on your fish, you can adjust the temperature and pH levels of your tank gradually over a few days. You can use an aquarium heater to lower the temperature and add pH adjusters to bring down the pH level. It’s important to monitor the pH and temperature regularly using a reliable testing kit and avoid sudden changes, which can stress your fish.

Tips for Maintaining Consistent Ammonia Levels

While it’s important to know how to lower ammonia levels when they become elevated, the best strategy is to maintain consistent levels at 0 PPM. Here are some effective methods for keeping ammonia levels in check in your aquarium.

Efficiently Cycling Your Aquarium

To maintain safe and consistent ammonia levels in your aquarium, it’s crucial to establish an efficient nitrogen cycle. The best way to achieve this is through a fishless cycle of your tank before introducing any fish.

Allow sufficient time for the cycle to complete, as it can take up to four weeks for the beneficial bacteria Nitrosomonas and Nitrobacter to establish and convert ammonia and nitrites into nitrate.

You’ll know that your tank is cycling effectively when the ammonia level reduces from 2 PPM to 0.2 PPM or lower within 24 hours. Once the cycle is complete, perform a partial water change to remove any excess nitrates and introduce fish slowly to avoid overwhelming the system.

Maintaining The Nitrogen Cycle

After successfully cycling your aquarium, it’s crucial to maintain the nitrogen cycle to ensure stable ammonia levels. Here are some actions to avoid that can disrupt the cycle:

  • Adding too many fish at once.
  • Overfeeding your fish.
  • Changing too much water at once.
  • Cleaning the filter too often.
  • Using chemicals or medications that can harm beneficial bacteria.

Instead, make gradual changes to the tank’s ecosystem, such as slowly increasing the number of fish, adjusting feeding habits, and changing water gradually. These measures will allow the bacteria to adjust and maintain a healthy environment for your fish.

Regular Tank Maintenance and Cleaning

In addition to cleaning your tank and filters on an alternating schedule, consider these tips to maintain low ammonia levels:

  • Perform weekly water tests to monitor ammonia levels and other water parameters, such as pH and nitrate levels.
  • Use a gravel vacuum to remove uneaten food and debris from the substrate.
  • Replace filter media gradually to avoid removing too much beneficial bacteria at once.
  • Avoid using soap or harsh chemicals when cleaning your tank or decorations, as they can harm beneficial bacteria and fish.

Regular Water Changes

Regular water changes are essential for maintaining a healthy aquarium. Water changes help reduce nitrate levels, but they can also be used to decrease the concentration of ammonia when it spikes. Even in a healthy tank, water changes are still important.

Before adding new water to the tank, test it for ammonia and pH levels. Use a water conditioner and pH adjusters to ensure that the water is at the appropriate level before performing the water change.

However, it’s worth noting that the exact frequency and volume of water changes required can vary depending on the size of the tank, the number and type of fish, and other factors.


Ammonia is dangerous to fish in your aquarium, and even a small amount of 0.25 PPM can harm them. The ideal level of ammonia for your fish is 0 PPM, which means you should strive for this level in your tank.

The nitrogen cycle is important for maintaining a healthy aquarium, so it’s crucial to start cycling your tank before adding any fish. While the terminology may be confusing at first, understanding the nitrogen cycle is essential for maintaining a balanced ecosystem in your aquarium.

Regular testing of ammonia levels will help you achieve a harmonious and healthy aquarium, ensuring that your fish are happy and healthy.

Leave a Comment