How to Lower & Remove Ammonia in Fish Tank?

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Perhaps you’ve noticed your fish beginning to display symptoms of ammonia poisoning, or you just happened to test your aquarium water and noticed the ammonia level was high, but you aren’t sure what to do about it.

In this article, we’ll take a look at all the different ways you can either lower or eliminate the ammonia in your tank.

how to lower ammonia in fish tank

When ammonia levels are too high, your fish may display one or several symptoms, such as a reddening of its gills, or swimming erratically and close to the surface.

In this case, you can use a variety of methods, such as changing the water and removing any detritus, in order to lower the ammonia levels.

Before we continue to the methods, let’s first take a look at why having ammonia in your fish tank is an issue and how it can occur.

Having Ammonia in Your Fish Tank

Ammonia is a naturally occurring gas with the chemical symbol NH3.

Ammonia is formed naturally in the human body and in fish and can be found in a variety of places in nature, such as in the water, soil, and air.

Ammonia is often used in industrial cleaning applications; however, it can be dangerous if absorbed back into the body, hence why it’s recommended for fish tanks not to contain any ammonia.

Here, we’ll take a closer look at the problem and from there, move on to how we can resolve it.

Causes of Ammonia in Your Tank

Some of the most common causes of ammonia in fish tanks include:

  • Usage of chloramine-treated tap water in your fish tank
  • Any buildup of detritus due to improper maintenance (including improper filtration)
  • Bacteria growth due to an abundance of detritus
  • Naturally produced ammonia by fish
  • A new tank where there aren’t enough beneficial bacteria to complete the nitrogen cycle

Signs of Having Too much Ammonia in the Tank

Besides regularly testing the water, these signs can tell you if you’re having too much ammonia in the fish tank as well, so be sure to pay attention to them:

  • When the ammonia has damaged the fish’s gills, they’ll feel the need to swim closer to the surface of the water to gasp for air
  • Fish may begin behaving sluggishly, sickly, or have trouble eating due to stress from a lack of oxygen
  • Ammonia can burn the gills and skin of fish, turning them a red or lilac color and eventually resulting in patches or streaks across their body
  • A lack of oxygen will result in the fish being disorientated and thus, swimming erratically in the water
  • Fish are scraping against objects in the hopes of alleviating the pain of the ammonia burns(ammonia poisoning)
  • Fish are laying on the tank floor with their fins clamped against their bodies due to a lack of energy

Is Having High Amounts of Ammonia Dangerous?

Having any amount of ammonia in a fish tank can be harmful to fish, with extremely high concentrations being capable of causing death.

As ammonia builds up in the tank, not only can fish have difficulty breathing, but they can have trouble eliminating the ammonia byproduct from their bodies.

This buildup in their bodies and the ammonia already present in the water can lead to stress, gill and internal organ damage, and finally the death of the fish.

How to Lower Ammonia in Your Tank

When you have high concentrations of ammonia in your aquarium and, especially if your fish are already being affected, the first thing you’ll want to do is to lower the impact of the ammonia in your tank. Here are several ways of doing so:

Add Commercial Ammonia Neutralizers to the Water

A quick way to lower the ammonia in the water is to add a commercially available ammonia neutralizer (i.e. ammo-lock or amquel) to the water. These products work by converting the toxic ammonia to non-toxic ammonium.

Keep in mind that this method doesn’t remove the ammonia, but simply neutralizes it so that it’s no longer toxic, hence lowering the effects that ammonia has on your fish. Biological filtration will still need to be present in order to convert the now-neutralized ammonia into nitrites and nitrates.

The key benefit of using these products is that the ammonia (though still present) will immediately cease to cause any harm to your fish while allowing the nitrification process to continue.

A drawback of this method, however, is that these products may produce false readings on your ammonia testing kits, making it difficult to determine when the nitrification process has been completed.

Reduce Feeding for the Fish

If you’ve noticed a lot of leftover fish food in the water, or if the fish is producing an unusually large amount of waste, it may be time to reduce the feeding for your fish.

Because leftover fish food and excess excrement both contribute to ammonia in the water, it may be helpful to reduce the amount of food you feed the fish.

Another good idea is to feed the fish in smaller increments; this way, you’ll have greater control of the food and how much you’re feeding, as opposed to if you were to feed one large meal to the fish.

Introduce Some Healthy Bacteria to the Water

Another method of lowering the amount of ammonia in the water is to introduce beneficial bacteria to the fish tank. Beneficial bacteria can come from a variety of sources, such as new fish, substrate from a previous tank, or a filter capable of biological filtering.

The bacteria are used to break down the ammonia into the much less harmful nitrites and nitrates (they are essential for the nitrification cycle). Some bacteria (i.e. Nitrosomonas) convert ammonia to nitrites, while others (i.e. Nitrobacter) convert nitrites to nitrates.

One thing to note is that you should refrain from adding too many fish at once, as this will cause a spike in ammonia that can offset what you’re trying to accomplish.

Lowering the pH of the Water

High Aquarium pH

Ammonia and high water pH tend to go hand in hand since ammonia has a harder time converting to nitrites in basic water conditions and is more toxic as well.

Hence, another option to lower ammonia levels is to buy some chemical pH adjusters at your local pet store.

Keep in mind that fish tend to prefer living within a certain pH range, so be sure to not lower the pH beyond that range.

Also, note that lowering the pH won’t actually remove the ammonia, but simply make the living situations more comfortable for the fish for the time being as the ammonia becomes less toxic.

The best thing to do would be to lower the pH as you’re removing ammonia so that the fish remains comfortable throughout the whole process.

You may also consider using gravel as your tank substrate instead of coral or sand, as the latter two can release calcium into the water, which may cause a rise in pH.

Increasing the Aeration of the Water

Having a running pump is a natural part of keeping your aquarium habitable to fish as it disturbs and introduces oxygen to the water so that fish and plants can flourish. Hence, it makes sense that another way to lower ammonia in the water is to increase aeration.

Increasing aeration will disturb the water more, allowing the ammonia to diffuse quicker into the air above the water, and provide more oxygen for the fish to breathe.

The only proper way to increase aeration is to use an efficient air pump. Of course, the stronger you set the pump, the more it aerates the water.

You may also consider using an air stone, however, this will not disturb the water; rather it’ll work as an oxygenator by only increasing the amount of oxygen in the water. While also beneficial to the fish, it won’t disperse the oxygen as well as an aerator would.

How to Remove Ammonia in a Fish Tank

Now that we’ve gone over the best ways to lower ammonia levels in your fish tank, let’s actually take a look at some of the methods used to physically remove ammonia from your tank.

Performing a Water Change

Possibly the quickest way of removing ammonia from your fish tank is to replace the old and ammonia-filled water with freshwater (otherwise known as a water change).

You may need to perform a series of partial water changes in order to dilute the ammonia to safer concentrations.

Partial water changes are normally something you should perform about once a week, where you replace about 10 to 15% of the water. However, if you’ve noticed a high concentration of ammonia in the water, you may need to perform more frequent partial water changes.

When performing these water changes, keep in mind the substrate may cloud up the water if you haven’t changed the water on a regular basis.

Therefore, to keep from disturbing the fish or plants when performing the water change, use a scoop or small bucket to replace the water instead of dumping out the water straight from the tank in one go.

Add the same amount of water you removed from the fish tank to a secondary location (i.e. a bucket), add some dechlorinating agents to the water, and let it sit for a few hours so that it becomes the same temperature as that in your primary tank before you pour it back in the tank.

Never change more than 30% of the fish tank water otherwise you’ll risk the loss of beneficial bacteria and may increase stress on the fish as they’re not used to so much newly added water.

Removing Waste and Any Other Organic Material

Another way to remove ammonia from your fish tank is to physically remove the things causing it. This includes dead plant matter, fish excrement, dead fish, leftover food, and any other forms of detritus in the tank.

In order to remove any detritus in the substrate, use a scoop or gravel filter. This will help remove a large portion of ammonia now and in the future.

You may also check the filter in your tank to make sure it’s not already filled with detritus, as an improperly functioning filter can disrupt the nitrification process. Make sure the filter is clean, replace the biological media, and check that the filter is the appropriate size for your tank.

Read More:


1. How Can You Lower Ammonia from A Fish Tank Naturally?

From what we’ve discussed earlier, here are some of the ways you may remove ammonia from your fish tank naturally:

  • Do a partial water change of about 30%. This is the quickest and most straightforward way of removing ammonia from the water, however, keep in mind that you should not change more than 30% of the water per week as that will get rid of a good portion of the beneficial bacteria and potentially disrupt the nitrification cycle
  • Remove any detritus you can find in the substrate or floating in the water using a scoop or gravel filter. This may include any rotting plant matter, dead fish, fish excrement, and leftover food
  • Reduce the amount of food you give to the fish. You may also consider feeding in smaller increments
  • Introduce beneficial bacteria that can more easily convert ammonia into less harmful nitrites and nitrates. This step may also be the first thing you do after you get a new tank
  • Increase the aeration and oxygenation levels in the water so that oxygen can enter the water and replace the ammonia

2. How Long Do the Beneficial Bacteria Take to Convert Ammonia Into Nitrites/nitrates?

The entire nitrification process might take roughly 2 to 6 weeks to complete in a new tank (this may take even longer in water below 70 degrees Fahrenheit).

However, you may be able to speed up this process if you add more beneficial bacteria to already existing bacteria in your well-established fish tank.

More details on the nitrification process may be found here.

3. How Long Does It Take for Ammonia to Affect Fish?

Although fish produce a significant amount of ammonia themselves, this is negated in the wild due to the large water-to-fish ratio, which allows much of the ammonia to be diluted. In an aquarium, however, you may find that the ammonia can build up to detectable levels within a few hours.

Although it may take several days for your fish to display any physical symptoms of ammonia poisoning, it’s best to take some water tests within a few hours of you running your aquarium, as even trace amounts of ammonia can be detrimental.


Having ammonia in your fish tank is certainly not desirable. However, with everything we’ve gone over today, hopefully, you’ll come to realize that the problem is far from unsolvable.

With early detection and management, you should have no trouble returning your aquarium to its former glory.

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