How To Lower Ammonia Levels In Fish Tank Naturally

Need to know how to lower ammonia levels in your fish tank? we cover the 7 best options, each covered in detail.

Ammonia is a huge problem in planted tanks as well as normal fish tanks too. In fact, it is highly poisonous to any and all living organisms in your fish tank.

It will quickly poison, eat away at, and eventually kill all of the plant and fish life in your aquarium. So, we are here today to help you figure out how to lower ammonia levels in your fish tank.

What Is Ammonia?

Ammonia is a colorless gas that has a very distinct odor. Ammonia is composed of both nitrogen atoms and hydrogen atoms, and it has the chemical symbol of NH3.

This is a naturally occurring substance that is produced by the human body, as well as in nature. It can occur in water, soil, air, and more.

Ammonia makes for a great cleaner, which is why it is used for many industrial cleaning applications, but that said, it is also poisonous, especially if the ammonia level in your fish tank hits a certain amount.

What Causes Ammonia In Fish Tanks?

aquarium nitorgen cycle

There are a variety of reasons why your fish tank might have high ammonia levels in it. If your aquarium has high ammonia levels, any of the following reasons may be to blame.

1. Uneaten Fish Food in the Aquarium

One of the biggest reasons as to why the ammonia level in your aquarium might be high is due to uneaten food. If uneaten food remains in the tank for too long, it will begin to rot and decompose.

As the uneaten food rots and decomposes, it creates and releases ammonia into the water.

Therefore, if you have an ammonia problem, feeding your fish less, cleaning the tank, and doing a water change to remove uneaten food can help.

2. Decaying Plants

Plants can also be a cause of a high ammonia level in a fish tank. If your plants are not doing well, those plants may start to rot or decompose in the tank.

If you have rotting plants in your tank, just like with uneaten fish food, those rotting plants will begin to create and release ammonia into the aquarium, which can then also lead to excessive ammonia nitrite levels as well.

To solve this issue, a water change can help, but removing decaying plant matter is the number one option.

That said, if you take good care of your plants and have them in the proper water parameters, then this really shouldn’t be a problem.

3. Excessive Fish Waste

If you have a fully stocked fish tank, one that has plenty of fish in it, especially if you feed them too much, they will create a lot of waste.

Fish waste, or feces in other words, is a leading cause of an excess ammonia level in the fish tank. Fish waste released a whole lot of this substance into an aquarium, and can quickly lead to an ammonia problem.

Once again, cleaning the tank and performing a water change can help, but feeding your fish less and ensuring that you have a working filter will help reduce ammonia levels in the tank the most, if this is the cause.

Many fish that eat a lot lead to excess waste, and therefore a big time ammonia level.

4. Improper Tank Filtration

Your aquarium filter is the number one tool at your disposal to get rid of ammonia in the tank. Your filter is a big part of the aquarium nitrogen cycle, particularly the biological filtration aspect.

Beneficial bacteria that grow in the filter actually break down ammonia in the tank by turning it into nitrite and nitrate.

If your filter is not up to handling the water volume in the tank, if you have many fish, if the filter is broken, if the biological media is old, or if you don’t properly clean and maintain your filter, it can quickly lead to this problem.

Excessive levels of ammonia can almost always be attributed to a lack of proper filtration in the tank.

To get rid of ammonia, cleaning your filter, replacing biological media, and ensuring that it is designed for your size of tank is crucial.

5. A New Tank – The Nitrogen Cycle in an Aquarium

The nitrogen cycle for aquarium is another big time player here, and the nitrogen cycle is perhaps the most important thing to remove ammonia from the tank.

If you have a new tank with new fish, the amount of beneficial bacterium in the tank will be lower than they should be. It takes between 3 and 6 weeks for these little organisms to multiply to the point where they can get rid of excessive levels of ammonia.

A new tank is always going to have excess levels of ammonia until the nitrogen cycle has completed a couple of times.

Therefore, to remove ammonia from the fish tank, waiting for a while for the cycle to get going is essential, and adding new fish to the aquarium before this is definitely not recommended.

Putting fish into a brand new tank like that will be a problem of its own, and yes, its due to the ammonia level.

6. Your Tap Water

Yes, your tap water may also have ammonia in it, so before you use water from the tap, make sure to let it sit for 24 hours.

Also, if need be, make sure to use water conditioner and ammonia remover before adding the water into the tank.

How Does Ammonia Affect Fish?

Simply put NH3 is highly toxic to fish. It causes chemical burns on the skin and on the gills, and as it absorbs in to the body of the fish, it literally burns them from the inside out.

It will burn interior tissue and organs, and end up causing mass organ failure, and eventually death.

What Should Ammonia Levels Be In My Fish Tank?

The level of ammonia in your fish tank should be as low as humanly possible. Fish are very sensitive to this stuff and even small amounts can cause a problem.

Always make sure to test the water to ensure that the levels are acceptable. 0 ppm is best, and remember that anything over 1 ppm (part per million), can be harmful to fish.

Therefore, the less there is, the better, and best is if there is none at all.

How To Lower Ammonia Levels In Fish Tank: 7 Ways

Now that we have covered what is ammonia in a fish tank let’s now look at 7 ways of reducing ammonia levels;

1. Changing The Water

One of the easiest, fastest, and most effective ways of decreasing ammonia levels in the water of your fish tank is to simply replace the old and contaminated water with fresh water.

To be fair, regular partial water changes is something that you should be doing on a weekly basis anyway. If you see that there is too much ammonia in the water, you can always perform the partial water changes more often.

One way to know that you aren’t doing these water changes often enough, is when you do them and the substrate (we have reviewed some good substrates over at this article), when stirred up, causes cloudiness in the water.

This is a sign that you aren’t doing the water changes often enough because there is clearly a lot of waste sunk in the substrate. Simply remove about 30 percent of the water with a scoop or small bucket, while being careful not to agitate the fish or destroy plant life.

Put the same amount of fresh water in a bucket with some dechlorinating agents, let it sit for a few hours, make sure the temperature is roughly the same as the current tank water, and slowly pour it back in.

In terms of numbers, this process should realistically take drop ammonia levels by 30%, or even more if you change more water. Keep in mind, it is not recommended that you ever change more than 30% of the water at once, or else you are putting the health of your fish at serious risk.

2. Remove Waste & Unwanted Organic Matter

Since rotting food, fish waste, and old plants can all cause ammonia, another easy solution to your ammonia problem is to remove the things creating or releasing it.

Of course you aren’t going to remove the fish from the tank, because they are the whole point of having an aquarium, but there are several other things that you can do for sure.

Use a scoop or gravel filter (this one is good) to clean the substrate of any and all waste, uneaten food, and decaying plant matter.

This will go a long way in lowering ammonia levels. Also, you can clean out the filter in your tank to make it more efficient at its job.

3. Less Feeding

If your fish leaves behind a lot of uneaten food, or if you realize that your fish produce an excessive quantity of waste when they shouldn’t be, it might be time to start feeding your fish less.

Since both uneaten food and fish waste release ammonia, feeding them no more than the required amount may help to reduce ammonia levels.

4. Healthy Bacteria

Another thing that you can try doing in order to lower the ammonia levels in your fish tank is to introduce some healthy and beneficial bacteria into the equation.

You can try adding some new fish into the water, adding gravel from an old tank, or get yourself a good filter with biological filtering, all of which will serve to add new bacteria into the water.

These bacteria will then break down the ammonia into nitrites, and eventually into nitrates. Both nitrites and nitrates are still harmful to your fish, but not nearly as much as ammonia.

5. Lowering The pH Level

When your water is basic, or higher up than 7.0 on the pH scale, ammonia tends to be present in higher concentrations because it does not break down as well is basic water. You can go to your local pet store and buy chemical pH adjusters to lower the pH levels in your fish tank.

Just beware that your fish do have a specific pH range which they need to live, so that is something you will need to take into consideration.

Lowering the pH levels in your fish tank will not actually remove the ammonia from the water, but it will make it less potent and dangerous to your fish.

You can actually also try adding new gravel into the tank as opposed to coral or sand. Coral and sand will release calcium into the water, which will in turn cause a rise in pH levels.

6. More Aeration

Having a lack of aeration in the water is bad not only for your fish as they try to breathe, but also because it allows ammonia to stay present in the water much easier. Ammonia is a dissolved gas, so a lack of aeration can make it stay in the water.

On the other hand, increasing the aeration will increase the rate at which the ammonia diffuses into the air above the water, thus decreasing the levels of it in the fish tank. The only way to really do this is by buying an air pump.

If you don’t have a pump then we have covered some other tips here.

7. Neutralizing Drops

The final thing that you can do in order to lower ammonia levels in your fish tank is to use neutralizing drops.

These will not actually remove the ammonia from the water, but they will render its toxic effects non-existent.

Signs Of High Ammonia Levels In Fish Tank

There are a few common signs to look out for such as;

  • Appetite loss
  • Gills inflamed (pink around gills)
  • Eyes inflamed
  • Labored breathing
  • Fish surfacing to the top more than normal

If you are in doubt then you should definitely do a test asap, you can either use test strips or a liquid test kit (we think liquid ones are better personally).

What Is The Best Ammonia Remover For Aquariums?

API AMMO-LOCK Ammonia detoxifier

This is one of the most highly rated ammonia removers out there, and it’s said to reduce ammonia in both water from the tap and your tank alike.

It can be used in both saltwater and freshwater tanks. All you have to do is pour it into the aquarium according to the instructions, and repeat the process every 2 days until there is no ammonia in the tank. It’s fast, simple, and very effective.


  • Very effective.
  • Easy to use.
  • A little goes a long way.
  • Clear instructions.


  • Excessive use is not healthy for fish.

Check pricing at Amazon

Commonly Asked Questions

How To Lower Ammonia Levels In Fish Tank Naturally

There are indeed various ways to naturally lower the levels of ammonia in a fish tank. Here is a quick overview of the most effective methods.

  • Do a partial water change of roughly 30%. This should automatically remove 30% of the ammonia content in the water. However, be careful not to change more than 30% of the water per week, as this can cause problems in itself.
  • Scoop out any and all organic matter that should not be present in the aquarium. This includes rotting plant matter, old food, fish waste, and dead fish as well.
  • Reduce the amount and frequency of food you give your fish. The less food they get, the less waste they produce, and this will therefore lower ammonia levels.
  • Introduce higher quantities of beneficial bacteria into the water which work to break ammonia down rapidly.
  • Slightly increase the aeration and oxygenation levels in the tank water.

How Do You Treat Ammonia Poisoning In Fish?

What you can do here is to prevent ammonia from building up in a fish tank in the first place. This is the most effective method.

However, unfortunately, there is absolutely no cure for ammonia poisoning in fish, which makes prevention all that much more important.

How Long Does It Take For Ammonia To Build Up In A Fish Tank?

Generally speaking, it is going to take anywhere between 30 and 45 days for ammonia to build up in a fish tank to levels which can harm and kill fish. This is pretty fast all things considered.

Of course, this is going to depend on several factors, including the amount of fish in the tank, the frequency and amount of feeding, if you have a good filtration system, how much oxygen is in the water, and how many beneficial bacteria you have present.

If conditions are not ideal in the least, it may take as little as 2 weeks for ammonia to build to levels that can be super harmful to fish.

How Long Does It Take For Ammonia To Go Down?

If you are experiencing an ammonia spike in your aquarium, it will take up to 6 weeks for it to go back down. Now, this does depend on the quality of the nitrogen cycle in your tank.

If you have plenty of beneficial bacteria in your tank that are breaking the ammonia down, it may take only 2 to 4 weeks, but if you don’t have beneficial bacteria, it will take much longer, or it might not go down at all.

This process can be quickened by adding more beneficial bacteria to the water and by doing regular partial water changes.

How Long Does It Take For Fish Food To Turn Into Ammonia?

This is another thing which depends great on tank conditions, mainly the amount of beneficial bacteria in the water.

Generally speaking, between the process of decomposition and the bacteria breaking food down, it will take about 2 to 4 days for uneaten fish food to turn into ammonia.

Is .25 Ammonia Harmful To Fish?

Technically speaking, any amount of aquarium ammonia can be harmful to fish. You should do everything in your power to prevent any and all ammonia from building up in the aquarium.

Ammonia levels of 0 parts per million are best. 1 part per million of ammonia in the water is still acceptable, although definitely not ideal. Anything over 2 parts per million has very real potential to harm your fish.

So, realistically, 0.25 ppm is not severe, and it should not harm your fish, but it is still worse than no ammonia at all.


Just remember that ammonia, even in the smallest of quantities, can end up making your fish sick and killing them very quickly so it’s important to know not only how to identify but also how to get rid of ammonia which hopefully we have helped you to do so.

It is important to test your water for ammonia on a regular basis, and if there is too much of it, use any or all of the above methods to rectify the situation.

Photo Credit: w:pl:Wikipedysta:Lukas3 / CC BY-SA

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