Quick Guide on How to Lower Ammonia Levels in Fish Tank (2024)

Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: July 6, 2024
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When setting up a fish tank, it’s essential to consider the water quality. Excessive amounts of certain chemicals like ammonia and nitrates can harm your fish’s health, as can low oxygen levels. It’s important to acknowledge that proper care, maintenance, and testing can prevent the harmful accumulation (or deficiency) of these critical chemicals in your fish’s habitat. We have gathered crucial advice, information, and support on how to reduce ammonia levels in fish tanks. Keep reading for further details!

Article Summary

  • Ammonia (NH3) is produced naturally in the fish tank through fish waste, organic matter breakdown, and uneaten food, and it can be harmful to your aquatic friends.
  • You can measure ammonia levels in your aquarium using an ammonia test kit, typically in the form of test strips.
  • To lower ammonia levels naturally, you can perform partial water changes, improve filtration, increase aeration, and consider upgrading to a larger tank if overstocked.

What is Ammonia?

Fish Tank With Tropical Coral Reef Aquarium
Tropical Coral Reef Aquarium

Known in the chemistry world as NH3, ammonia is produced naturally in the fish tank through fish waste, as well as the breakdown of organic matter such as dead fish, dead plants, and uneaten food.

In the terrestrial environment this nitrogen is important to the growth of plants as part of the nitrogen cycle, but in your fish tank it can cause nothing but problems!

Measuring Ammonia Levels

Ammonia levels are typically measured using an aquarium test kit, which can let you know exactly how much ammonia is present in your fish tank along with checking the pH scale of your water.

In most instances this ammonia test kit consists of a simple strip which you dip into your tank, which then produces a color of varying grade

Beneficial Bacteria

In normal circumstances, there are beneficial bacteria in the fish tank which can get rid of ammonia over time.

However, when there is too much ammonia for this natural system, it can lead to serious problems for your fish and aquarium plants such as toxic shock.

The process of ammonia reduction by beneficial bacteria actually produces its own harmful byproduct, known as nitrates, which are then broken down in turn by a second group of good bacteria.

Water Test Kits

Ammonia and nitrite are two things that most test kits will measure, as they can both negatively impact the health of your aquarium when left unchecked.

This two-step biological filtration process of the aquarium nitrogen cycle is incredibly important when designing and maintaining a healthy tank in the long term, as it may take time for each of these healthy bacteria to reach the appropriate level in your aquarium.

Why is it Important to Reduce Ammonia in Your Aquarium?

When your tank becomes cloudy and has an ammonia problem, your fish will likely be the first affected.

Initially it may be hard to notice, but over time the symptoms of ammonia poisoning will become more and more hard to avoid, until it can be too late and they die of toxic shock.

The signs and symptoms of this incredibly painful illness are listed and described later on in the article, but suffice it to say it’s not pretty!

Additionally, it’s not just the fish but the plants, invertebrates, and eventually even the bacteria who get harmed by all the ammonia present in your tank.

None of these organisms work well in this type of dangerous environment, and lowering the nitrite and ammonia level to a safe metric of 0ppm is important for the health of all of your aquatic friends.

Where Ammonia in Fish Tank Comes From

Small Goldfish Aquarium
Small Goldfish Aquarium

Fish waste (ie feces) will naturally release ammonia, and can accumulate rapidly over time without a proper filtration setup and water flow in your tank.

Considering that each fish (as well as the invertebrates in your tank!) produces its own separate amount of waste, we have to look at just how much of each is actually appropriate for the tank we want in order to keep the ammonia level down.


It’s important to consider just how many fish you want to have in your tank at one time when first setting up your aquarium, as too small of a tank with too many fish can quickly lead to elevated ammonia levels..

Ammonia from uneaten food

Uneaten food produces ammonia as well. While some people like to think that they’re doing their fishy friends a favor by throwing a little extra in at feeding time, this extra food will likely go uneaten and begin to break down rapidly.

Over time, the food releases ammonia into the water as it breaks down, contributing to the overall ammonia level in the fish tank.

Remove Uneaten Food

When feeding fish, and especially when feeding them something that they may never have had before such as human foods, try to remove any uneaten food that is still present inside the tank after 30 minutes have passed.

This will ensure that the uneaten fish food isn’t missed and doesn’t wind up becoming another cause of a high ammonia level in the fish tank.

Dead Organisms

Dead plants, invertebrates, and fish produce ammonia as well when they begin to decay. Dead fish are usually pretty easy to spot, and will either sit motionless on the bottom of the tank, or begin to float towards the surface.

Over time, they’ll produce a nasty smell and may begin to bloat as they fill with ammonia gas, so it is best to remove the dead fish from the aquarium as soon as possible.

While it’s typically obvious to notice our once-live friends no longer moving, with invertebrates it can be a bit trickier.

Check for signs of life

If you have something like a snail or other slow-moving critter, try to make note of where it is in the tank if you suspect something.

If after a few hours it still hasn’t moved, try to poke it for a reaction. If still not seeing any movement after a day or two, consider removing the poor creature from the tank to reduce ammonia risk.

Other Causes of High Ammonia Levels

Fish Near Filter Tube
Fish Near Filter Tube

In addition to the natural causes of ammonia such as dead and decaying organic matter and fish waste, there can be some artificial causes of the aquarium ammonia being too high as well.

Several different factors can each lead to potentially high levels of ammonia, and are usually fairly easy to remedy with proper attention to detail.


Too little filtration power can be a major cause of ammonia buildup in the tank…

The best way to ensure that you meet the proper needs of your particular setup is to talk to your local pet store, or wherever it is that you’re purchasing your fish, and determine their individual needs regarding waste production

In a pinch, ammonia-specific filter pads can provide a quick method of reducing ammonia levels.

However, it’s unlikely that when an emergency actually happens you’ll be able to find one lying around, so make sure to place them somewhere easily accessible!

Additionally, be sure to remove expended pads and filter media once they’ve made it through their cycle of use (which is usually stated somewhere on the packaging.)


In general, a larger tank will require stronger filters in order to reduce ammonia levels to that proper 0 parts per million and keep those healthy fish safe in the long run.

Cycling tank water

Cycling your water is a way of jumpstarting a new tank by introducing some form of ammonia, be it through drops, food, or even dead matter, in order to start off those beneficial bacteria in the process of the nitrogen cycle.

However, if this cycle is still happening when you first add your fish it can lead to high ammonia levels that are dangerous for them.

Here’s an informative video about fish tank water cycling

How to Cycle a Fish Tank FAST!

Allowing your tank to properly cycle through the initial processes of the nitrogen cycle is key to a healthy tank.

This process involves ammonia levels rising and falling over time as they are converted to nitrites. Again remember that it takes time for the beneficial bacteria to reach their maximum reducing capacity, so be patient!


With more fish comes more waste! Putting too many fish in too small of a space, or too many at one time can be dangerous. Your tank’s bacteria need time to adjust the levels of ammonia and nitrates to safe levels, otherwise they can become overwhelmed.

Most fish have a specific amount of gallons of water that they require in order to prevent ammonia poisoning, and exceeding this limit is a sure fire way to create an ammonia problem in your tank.


Make sure to do your research when looking into the fish and invertebrates you’d like to add. Dumping water and animals into the tank all at once and hoping for the best is a sure way to create future problems!

How Ammonia Affects Fish in Fish Tanks

Fish Swimming Close
Fish Swimming Close

As an invisible opponent, it can be hard to see ammonia at work in the tank.

However, over time and with too high of an ammonia level, you’ll begin to see your fish behaving in odd ways, showing signs and symptoms of ammonia shock, which are described later in the article.

The natural cellular processes that most organisms use to stay alive (such as respiration, circulation, and digestion) can’t handle this high ammonia level and will begin to break down over time.

This may present as altered behavior, painful looking discoloration, fins rotting, and eventually the death of your fish and other organisms in the tank.

What is The Acceptable Ammonia Level in a Fish Tank?

The answer to this is 0 parts per million of ammonia to water within the tank. While we may wish that we could have some leeway in this metric, it’s important to note that even levels as low as 2ppm can lead to serious harm for your fish.

The bare minimum that could be survivable above this 0 benchmark is 0.5, but even this is still cutting it dangerously close to toxic levels.

This rule goes for both saltwater and freshwater aquariums, as both types of fish still require a safely low to not-present level of ammonia in order to live a healthy life.

In fact, marine organisms in a saltwater tank are more likely to be sensitive to fish adapted to freshwater, who have grown to be more adaptable to the variable conditions in lakes and ponds

How to Lower Ammonia Levels in Fish Tank Naturally

If all of the negative consequences sound rather dire and hard to remedy, don’t worry! There are quite a few options when one wants to get rid of ammonia in their aquarium water. These include:

Partial Water Change

Aquarium Water Change
Aquarium Water Change

Considered a part of a typical care regimen regardless of high ammonia levels, water changes are a quick and easy way to drop the ammonia level in your tank.

The general principle is to take out some of the old water and add in new, freshwater but there are a few key things to keep in mind with a partial water change.

  1. The first step is to remove around 30% of your tank water, preferably without disturbing the bottom and kicking up any harmful substrates along with not harming any of your fish in the process.
  2. Next, take that same amount of freshwater (this can even be tap water,) adding in water conditioner, and allow it to reach the same temperature as the water in the rest of the tank.
  3. Lastly, add this water back into the tank and you’re good to go!

Hopefully, this 30% swap should create at least a 30% reduction in the aquarium ammonia level, and can be done multiple times to see more of a decrease.

Improve the Filtration

Another option that is relatively quick and easy is simply beefing up the existing filtration in your tank, typically by purchasing stronger filters, or potentially adding more. Improving the filtration of your tank not only reduces ammonia buildup but also lessens algae blooms in your fish tank.

Look at whatever aquarium filter you already have and determine if you’d like to simply purchase more of the same, or consider replacing it all together with something more effective.

Increase Aeration

Adding air pumps, air stones, and bubblers can increase the amount of water flow through your tank, upping the oxygen levels while causing settled sediments to be moved more rapidly through your filters.

Considering that ammonia itself is a dissolved gas, adding in more air flow can allow this to move up and out of your tank through the surface.

Upgrade to a Bigger Tank

If you have more fish than the size of your tank can handle, a somewhat longer term solution can be to start the process of developing beneficial bacteria over again with a new tank that is a better fit for your fish.

The Non-Natural Way: Neutralizing Drops

Neutralizing Drops

With just a few drops, these wonders can serve to protect your fish from the harmful effects of ammonia poisoning when levels have gotten too high.

As an important note, these are not actual ammonia removers, but each drop detoxifies ammonia already present in the tank.

Think of these as chemical pH adjusters, rather than a way to reduce ammonia itself.

How to Lower Ammonia Levels in a New Fish Tank

Aquarium Without Fish
Aquarium Without Fish

In a new fish tank, it’s important to start things off by cycling nitrogen through your tank and allowing the beneficial bacteria to begin the processing of lowering ammonia levels naturally.

Artificially causing an ammonia spike may seem silly, but this will signal the beneficial bacteria present in the substrate of your fish tank that it’s time to kick off the nitrogen cycle, and they’ll begin reducing this into nitrates.

This, in turn signals other beneficial bacteria to begin further reducing that nitrate present in the fish tank to a safe level.

These nitrifying bacteria are a critical component, and it’s important to make sure that they have the proper amount of time to fully reduce the ammonia in a fish tank to nitrate and nitrite before proceeding.


Ensuring that this whole cycle has time to complete several times over(typically over the course of 3-6 weeks,) is critical before adding any additional fish into your fish tank and potentially overwhelming the beneficial bacteria.

How To Lower Ammonia Levels in a Freshwater Fish Tank

All of the above methods can be used, and pay special attention to your fish when using tap water.

Some cities may have different allowances with regards to levels of chemicals such as fluoride and chlorine, which may necessitate the use of dechlorinating agents and other water treatment.

How To Lower Ammonia Levels in a Saltwater Fish Tank

Similar to a freshwater tank, most of the above methods can be used. However, you will need to use additional aquarium salt additives when replacing the water in your tank.

Also be aware that many tropical fish are extra sensitive to changes in the water parameters of your tank and may need to be put into a separate fish tank while your original tank adjusts and reaches safe levels of ammonia.

How Long Does it Take to Get Ammonia Levels Down in a Fish Tank?

In most cases, it will take around 6 weeks for an ammonia spike to settle down to acceptable levels in your tank.

With an efficient biological filter of good bacteria, this can be as little as 2-4 weeks, but it requires patience to fully remove ammonia in a fish tank.

Symptoms of Ammonia Poisoning in the Fish Tank

Ammonia poisoning can look like many other illnesses amongst fish, but there are a few key symptoms to keep an eye out for when assessing the health of your fishy friends.

  • Lethargy – Fish may seem to be moving slowly, or not at all. This is not uncommon during the colder seasons if you have a cold water tank, but when persisting for longer than a few days can be a sign of something wrong.
  • Loss of appetite – Another reason it is important to monitor your fish for 30 minutes after feeding aside from removing uneaten food is to make sure that they’re eating at all
  • Gasping at the surface – This odd behavior is a typical sign of fish distress, as they are attempting to get more oxygen into their system than they currently have
  • Inflamed gills – Reddish, swollen fish gills are a sign that the water quality is reaching unsafe levels and the organs of the fish are becoming damaged by the presence of ammonia in the fish tank.
  • Red streaks or inflammation in the fins
  • Inflamed eyes or anus

Can You Cure Ammonia Poisoning in Fish?

Unfortunately there is no known cure for ammonia poisoning in fish, as well as for the aquatic plants in your tank. The best that we can hope to do is reduce the levels before they show symptoms in the first place.

If they are showing symptoms, it’s best to just monitor them for further health complications until removing them after they pass.


As we’ve seen throughout today’s article, while a high ammonia level in your fish tank can be a serious problem there are several ways to remove and prevent it.

Fostering beneficial bacteria, removing organic waste such as dead fish and old fish food, and adding additional filtration are all a good start, with consistent partial water change providing a good measure of ammonia reduction.

Feel Free To Share!

As always we hope that you’ve enjoyed today’s article and that it has helped you figure out how to solve your ammonia problems.

If you found this information useful, feel free to pass it along to other fish fanatics in your life and we wish you good luck on your aquarium adventures!

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