How to Lower Ammonia in Fish Tank?

If you own an aquarium, knowing how to lower ammonia levels is crucial for maintaining a healthy environment for your fish. Ammonia can be harmful and even fatal to your aquatic friends. In this article, we will explore the dangers of ammonia, its causes, and various methods you can use to reduce ammonia levels in your fish tank.

lower ammonia in fish tank

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What are the Dangers of Ammonia for Aquarium Fish?

Ammonia is a toxic compound that can have detrimental effects on your fish. High levels of ammonia in your fish tank can cause severe health problems, stress, and even death in your aquatic pets.

Ammonia poisoning can manifest in fish through various symptoms, such as:

  • Lethargy and unusual movements
  • Red or inflamed gills
  • Gasping for air at the surface
  • Excess mucus production on body and gills
  • Loss of appetite and weight
  • Fading or darkening of colors
  • Lesions and ulcers on skin

Ammonia burns fish gills and impedes respiration, which leads to oxygen deprivation. At high concentrations, ammonia can cause significant damage to the fish’s nervous system, ultimately resulting in death.

In addition to its direct impact on the fish’s health, ammonia can also lead to secondary complications such as infections and parasites. When fish are stressed by high ammonia levels, their immune systems become compromised, making them susceptible to these issues.

What is Ammonia in the Aquarium Nitrogen Cycle?

Ammonia is a toxic compound that forms a crucial part of the aquarium nitrogen cycle. It is naturally produced in fish tanks as a result of fish waste, decaying plants, uneaten food, and other organic materials.

The aquarium nitrogen cycle, also known as the nitrification process, is a vital biological process that occurs in the fish tank to convert harmful ammonia into less toxic compounds. In this process:

  1. Ammonia (NH3) is produced as a byproduct of fish waste, uneaten food, and decaying plants.
  2. Beneficial bacteria, called Nitrosomonas, break down ammonia into nitrite (NO2-), which is still harmful to fish.
  3. Another group of beneficial bacteria, called Nitrospira, convert nitrite into nitrate (NO3-), a much less toxic compound for fish.
  4. Eventually, a process called denitrification occurs, in which nitrates are reduced into nitrogen gas (N2) by anaerobic bacteria, which then escapes the water surface, completing the cycle.

For aquarium hobbyists, understanding and maintaining a healthy nitrogen cycle is essential to ensure the well-being of the fish and other aquatic inhabitants. High levels of ammonia in the fish tank can lead to deadly consequences for your fish, as it can damage their gills, leading to difficulty in breathing, and can even be fatal in severe cases.

To lower ammonia levels in your fish tank, you need to maintain a proper nitrogen cycle to ensure a balanced ecosystem. 

This can be achieved through the various methods and techniques mentioned later in the article, such as fishless cycling, adjusting fish stocking, reducing feeding, using ammonia-absorbing plants, and maintaining regular water changes and proper filtration.

What are the Causes of High Ammonia in Fish Tank?

Understanding the main causes of high ammonia levels in a fish tank is crucial for maintaining a healthy environment for your aquatic pets. There are several factors that can contribute to elevated ammonia levels, and knowing them will help you identify and resolve the problem effectively.

  • Overstocking: Having too many fish in your tank can increase the production of waste, leading to higher ammonia levels. Keep the fish population in check by only adding the appropriate amount of fish for the tank’s size and filtration capabilities.
  • Overfeeding: Excess food in the tank can break down and release ammonia as it decomposes. Feed your fish appropriate portions and remove any uneaten food to control ammonia levels.
  • Poor filtration: A poorly maintained or undersized filter can fail to adequately process ammonia in your aquarium. Regularly clean your filters and make sure they are appropriate for your tank size and fish population.
  • Insufficient beneficial bacteria: Nitrosomonas and Nitrobacter bacteria play a crucial role in breaking down ammonia in the nitrogen cycle. Ensure that these bacteria are present and flourishing in your tank, either through “cycling” the tank or adding commercially available bacterial cultures.
  • Decaying organic matter: Dead plants, fish, and other waste can break down and release ammonia. Regularly remove decaying organic matter from your tank to avoid ammonia spikes.
  • New tank syndrome: New tanks often experience an increase in ammonia levels before the nitrogen cycle can be established. Give your new tank enough time to establish a stable nitrogen cycle before adding a full fish population.

Being aware of the causes of high ammonia in your fish tank is the first step towards creating a healthy and stress-free environment for your aquatic pets. With proper care and maintenance, you can prevent and control ammonia levels, ensuring your fish live happy, healthy lives.

What Methods to Use to Lower Ammonia in Aquariums?

There are several effective methods to help you reduce ammonia levels in your fish tank, ensuring a healthier environment for your aquarium inhabitants.

Here are 7 approaches to lower and eliminate ammonia in your fish tank:

– Fishless Cycling: Before adding any fish to your new tank, perform fishless cycling to allow beneficial bacteria to colonize the filter media and convert ammonia into nitrite and nitrate, which are less toxic to fish. To do this, add a source of ammonia (e.g., liquid ammonium chloride or a small piece of fish food) and a bacterial starter to the tank, then regularly test the water until ammonia and nitrite levels are undetectable.

– Adjust Fish Stocking: Overstocking your tank can lead to high ammonia levels. Make sure you have the appropriate number of fish for the size of your aquarium. If necessary, consider removing some fish to reduce the bioload and the amount of ammonia produced.

– Reduce Feeding: Overfeeding your fish can result in leftover food and increased waste, both of which contribute to high ammonia levels. Feed your fish small amounts of food, only as much as they can consume within a few minutes, and remove any uneaten food afterward.

– Use Plants that Absorb Ammonia: Live plants, such as Amazon swords and marimo moss balls, can naturally absorb ammonia from the water. Including these in your tank can help reduce ammonia levels.

– Regular Water Changes: Perform partial water changes (20-30%) every one to two weeks, depending on the tank size and bioload, to dilute ammonia and prevent its build-up in the fish tank.

– Enhanced Filtration and Filter Media: Opt for a high-quality biological filtration system, and use filter media, such as ceramic rings or bio-balls, to promote beneficial bacteria growth, which aids ammonia reduction.

– Chemical Filtration: Use specialized filter media, like zeolite or activated carbon, for chemical filtration to absorb ammonia from the water and lower its levels. Replace the chemical filtration media regularly to maintain its effectiveness.

Fishless Cycling

Fishless cycling is a popular method to establish the nitrogen cycle in a new aquarium before adding fish. It involves adding ammonia to the aquarium, allowing beneficial bacteria to convert the ammonia to nitrites and then to nitrates, which are relatively less harmful to fish.

  • The first step in fishless cycling is to set up your aquarium completely, including filter, heater, and decorations. Make sure that everything is in place and working properly.
  • To kickstart the process, add ammonia to your tank. You can either use pure ammonia or a specially designed ammonium chloride solution, which can be found at aquarium stores.
  • It’s essential to monitor ammonia, nitrite, and nitrate levels throughout the fishless cycling process. You can do this by using water testing kits that are readily available at aquarium stores.
  • Once ammonia levels start to decrease and nitrite levels increase, this signifies that the first group of bacteria have established in your tank. After some time, nitrite will also start to decrease, indicating the presence of a second group of bacteria converting nitrite into nitrate.
  • Continue testing and adding ammonia until both ammonia and nitrite levels reach zero and nitrates are present in the water. This indicates that the nitrogen cycle is complete, and your tank is ready for fish!

Fishless cycling takes about 4-6 weeks on average, but patience is key. By taking the time to properly cycle your aquarium using fishless cycling, you create a healthy and stable environment for your fish, and ultimately, prevent the buildup of harmful ammonia.

Adjust Fish Stocking

One effective way to lower ammonia levels in your fish tank is to adjust the fish stocking. Since fish waste is a major contributor to ammonia production, it makes sense to manage the number of fish in your tank to balance the ecosystem naturally. To achieve this, consider the following steps:

  1. Evaluate your current fish population: Look at the size of your fish tank and the types and sizes of fish you have. A common guideline is to allow about 1 inch (2.5 cm) of fish per gallon of water, or 1 cm of fish per liter of water.
  2. Remove excess fish: If your tank is overstocked, consider relocating some of the fish to a different tank or giving them to a fellow aquarist. Reducing the number of fish will immediately decrease the amount of waste in your tank, leading to lower ammonia levels.
  3. Avoid overstocking: It may be tempting to add more fish to your tank, but doing so can put stress on the existing ecosystem and cause a spike in ammonia levels. When adding fish, do so gradually and make sure to monitor the ammonia levels closely.
  4. Select appropriate fish species: Some fish produce more waste than others, which can rapidly increase the ammonia levels in your tank. Opt for fish species that are known to produce less waste or are more tolerant of higher ammonia levels, such as tetras, guppies, and mollies.

By adjusting fish stocking in your tank, you can effectively lower ammonia levels and maintain a healthy environment for your aquatic friends. Remember to routinely monitor the ammonia levels to ensure the wellbeing of your fish and the overall balance of your aquarium ecosystem.

Reduce Feeding

One of the easiest ways to lower ammonia levels in your fish tank is by reducing the amount of food you give to your fish. Overfeeding can lead to excess food waste, which decomposes and produces ammonia as a byproduct, putting your aquatic friends at risk.

  • Feed your fish only what they can consume within a few minutes. It’s better to provide smaller, more frequent meals rather than large portions all at once.
  • Monitor the fish’s eating habits to ensure they are getting enough nutrients, but without leaving uneaten food behind.

Adjusting your feeding practices not only helps control ammonia levels but also prevents other water quality issues and maintains the overall health of your fish. Reducing the amount of food you give your fish will lower the amount of waste produced, which in turn reduces the ammonia concentration in the tank. Getting the right balance can be tricky, but here are a few tips:

  • Use high-quality, nutrient-dense fish food to ensure your fish receive sufficient nourishment while minimizing waste.
  • Remove uneaten food after a few minutes to prevent it from decomposing and releasing ammonia in the tank.
  • Gradually decrease the amount of food you offer until you reach the optimal level for your specific fish species and tank size.

By feeding your fish more responsibly, you can help maintain a cleaner and safer environment for them while reducing the risk of ammonia spikes. Remember that the key is to find the right balance between nutrition and waste management to keep your fish healthy and your aquarium thriving.

Use Plants that Absorb Ammonia

Incorporating live plants into your aquarium is a natural and effective way to combat high ammonia levels. Aquatic plants are known to consume ammonia as a part of their metabolic process, which helps maintain a healthy and stable environment for your fish.

Some of the best plants for absorbing ammonia include:

  • Amazon Sword: A popular option, this hardy plant is a fast grower and will help break down wastes, such as ammonia.
  • Anubias: A slow-growing but very tolerant species, it can survive in a wide range of water conditions and help filter ammonia.
  • Hornwort: With its rapid growth, hornwort will take up a lot of ammonia. Additionally, it does not require substrate, so it can float freely or be anchored.
  • Water Sprite: An easy-to-grow plant that propagates quickly, the water sprite is great for absorbing ammonia and other nitrogenous compounds.
  • Duckweed: This fast-growing floating plant works well to consume ammonia, but it can be invasive; ensure you control its growth.

Always remember to go for healthy plants to provide the best filtration and overall wellbeing of your aquarium. When choosing plants, always consider the type of fish you have, their behaviors, and the size of your tank, as certain plants will work better depending on the specific species.

After you’ve incorporated plants, monitor your tank’s ammonia levels to ensure healthy conditions for your fish. Through this natural approach, you’re helping to create a stable environment that benefits both the fish and the plants, leading to a thriving aquatic ecosystem.

Regular Water Changes

A crucial aspect of maintaining a healthy fish tank and lowering ammonia levels is performing regular water changes. By replacing a portion of the water in your aquarium with fresh, clean water, you can effectively dilute the concentration of ammonia as well as other harmful substances.

Here’s a step-by-step guide to performing regular water changes:

  1. Determine the appropriate water change frequency – Depending on the size of your fish tank, the number of fish, and the efficiency of your filtration system, you might need to perform water changes every week or every two weeks. As a general rule, consider changing 10-25% of the tank water each time.
  2. Prepare the fresh water – It’s important to use dechlorinated tap water or premixed aquarium water, adjusted to the appropriate temperature and pH levels to match your aquarium.
  3. Turn off any equipment – Before starting the water change, switch off your aquarium’s heater, filter, and any other devices to avoid damage.
  4. Remove and clean decorations and accessories – Gently remove any large ornaments, plants, or other decorations from the tank, and clean them properly to remove algae and other buildup.
  5. Siphon out the old water – Use a gravel vacuum or siphon tube to remove water from the tank, allowing the vacuum to remove debris that may have gathered in the gravel.
  6. Refill with the prepared fresh water – Carefully pour the fresh water into the tank, preferably using a container with a spout or a hose to disturb the substrate as little as possible.
  7. Turn the equipment back on – After refilling, switch your aquarium equipment back on and ensure their proper functioning.

Remember, regular water changes are essential to maintain a healthy environment for your fish and keep ammonia levels low. Always test the ammonia concentration before and after water changes to ensure the effectiveness of your efforts.

Enhanced Filtration and Filter Media

An important aspect of lowering ammonia levels in your fish tank involves enhancing the filtration system and utilizing the appropriate filter media. The primary purpose of a fish tank filter is to break down harmful substances such as ammonia and nitrite, which are toxic for aquatic organisms. To achieve this, consider the following:

  • Upgrading your filter system: If your current system is not efficient enough or is too small for your aquarium, upgrading to a larger and more powerful filtration system is essential. A high-quality and larger filter can increase its ability to process ammonia, thus improving the water quality for your fish.
  • Selecting appropriate filter media: The filter media plays a crucial role in maintaining a healthy aquarium environment by providing a surface for beneficial bacteria to grow and thrive. These bacteria help in breaking down ammonia into less harmful substances. Common types of filter media include:
    • Mechanical media: Removes solid waste and debris from the water. This includes sponge filters, foam pads, and filter floss.
    • Biological media: Provides a surface for beneficial bacteria to grow, which can break down ammonia and nitrite. Examples are ceramic rings, bio-balls, and lava rock.
    • Chemical media: Absorbs or neutralizes harmful substances in the water, including ammonia. Zeolite and activated carbon are popular options for chemical filtration.
  • Regular maintenance: Clean and replace filter media as needed to maintain the effectiveness of your filtration system. However, avoid cleaning all the media at once, as this can disrupt the established beneficial bacteria needed for ammonia breakdown.

Enhanced filtration and the appropriate filter media are essential for controlling ammonia levels in a fish tank. Upgrading your filter system, choosing the right filter media, and regular maintenance will help create a healthier environment for your fish.

Specialized Chemical Filtration

Chemical filtration is an effective way of lowering ammonia levels in your fish tank. This method utilizes specialized filter media that target specific chemicals or elements, such as ammonia, to keep water quality in check. There are multiple options for chemical filtration products that can be useful for ammonia control:

1. Ammonia Removers

Ammonia removers are products specifically designed to lower ammonia levels in an aquarium. These can either be added directly to the water or placed inside the filter system, depending on the product you choose. Common ammonia removers include:

  • Zeolite – A naturally occurring mineral that traps ammonia ions, often used as a filter media.
  • Activated carbon – Absorbs ammonia and other impurities from the water, and can be placed in a filter bag within the aquarium filter.
  • Sodium thiosulfate – A chemical that neutralizes ammonia, available as a powdered or liquid solution.

2. Ion-exchange Resins

Ion-exchange resins are specially formulated synthetic materials that help remove nitrogen waste products, including ammonia, by binding to them and preventing their re-release into the water. To use ion-exchange resins:

  • Add the resin to your aquarium filter, following the manufacturer’s instructions.
  • Replace the resin regularly, as its effectiveness will reduce over time.

Remember that chemical filtration should be used as a temporary solution and not be relied upon to maintain consistently low ammonia levels. You’ll need to continue regular water changes and other ammonia-reducing efforts for long-term success with your fish tank.

Chemical filtration can efficiently address elevated ammonia levels in a fish tank, helping to maintain a safe and healthy environment for your aquatic pets. Choose from various products and filter media to create the perfect ammonia-reducing solution for your tank.

How to Monitor and Test for Ammonia in Fish Tank?

Monitoring and testing the ammonia levels in your fish tank is crucial to maintain a healthy environment for your aquatic pets. Regular testing will help you identify ammonia problems early on and ensure that you take the necessary steps to lower ammonia levels before they become a danger to your fish’s health.

There are various methods to test the ammonia levels in a fish tank, including:

  • Liquid test kits: These kits typically include a test tube, a reagent (chemical solution), and a color chart. To use the kit, fill the test tube with water from your aquarium, add the required drops of the reagent, and then compare the resulting color with the chart provided. The color will indicate the ammonia level.
  • Test strips: These are easy-to-use strips that you simply dip into the aquarium water and then compare the resulting color with the chart provided. Test strips generally have a shorter shelf life than liquid test kits.
  • Electronic monitors: These devices allow for continuous monitoring of ammonia levels in the fish tank. Some also have the added benefit of alerting you with an alarm or k a visual indicator when ammonia levels rise above an acceptable level.

To maintain a healthy fish tank, test your aquarium water every week and after any significant changes, such as adding new fish, performing a water change, or modifying the filtration system. Make sure you record your ammonia test results to track any changes over time and adjust your tank maintenance routine accordingly.

Regular monitoring and testing for ammonia in your fish tank are essential for maintaining a healthy environment for your aquatic pets. Make sure you use the appropriate testing methods and maintain a consistent tank maintenance routine to keep ammonia levels in check.

Why do new fish tanks frequently have ammonia spikes?

New fish tanks often experience ammonia spikes due to lack of beneficial bacteria and the Nitrogen cycle not being established yet. As the aquarium gradually acquires a proper balance of beneficial bacteria, ammonia spikes will become less frequent and less severe.

Why do some fish seem unaffected by high ammonia levels?

Some fish can tolerate higher levels of ammonia due to their natural habitat conditions or physiological adaptations. However, this does not mean that such conditions are ideal for the fish; prolonged exposure to high ammonia levels can cause health issues and stress.

How long should I wait to add fish after treating my tank for high ammonia levels?

Generally, wait for at least 24 hours after treating your tank for high ammonia levels, and ensure that the ammonia levels are consistently low before adding more fish. Keep monitoring the ammonia levels to ensure stability.

How can I tell if my aquarium has too much ammonia without a test kit?

While using a test kit is the most accurate way to measure ammonia levels, you might first notice behavioral and physical changes in your fish, such as gasping for air, erratic swimming, and discoloration. These could be signs that your ammonia levels are too high and should be tested and addressed.

Can I use a water conditioner to neutralize ammonia in my fish tank?

Yes, certain water conditioners can help neutralize ammonia in your fish tank by transforming toxic ammonia into a less harmful form. However, it’s important to keep in mind that using water conditioners is just a temporary solution and does not address the root cause of the ammonia issues.


Maintaining a healthy and stable environment for your fish is crucial to their well-being and longevity. By understanding and controlling ammonia levels in your fish tank, you can keep your aquatic friends healthy and stress-free. We hope you found this information helpful, and feel free to leave a comment or share your own tips for maintaining a safe aquarium.

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