Ammonia Poisoning In Goldfish (Why It’s So Dangerous)

Ammonia poisoning can be a problem for most fish. It’s important to understand that when owning Goldfish, there is a range of things that can affect them, and we need to understand the right way of caring for them.

Ammonia poisoning can be detrimental to your Goldfish, so we need to understand how it can happen, how to treat it but also how to prevent it in the first place.

What Is Ammonia Poisoning?

Ammonia is an organic compound gas made up of nitrogen and hydrogen atoms. Small amounts of exposure to ammonia to your Goldfish will not be life-threatening but will cause issues. However, in larger quantities, it is a serious problem.

As one of the biggest killers for fish, ammonia poisoning is most common when setting up your new tank. It can be due to your fish being exposed to incorrect pH levels, which then makes your Goldfish ill, as we know they need to live in certain conditions to thrive.

Ammonia poisoning is the negative effect of ammonia not being converted into the nitrogen cycle. The nitrogen cycle is critical for a healthy tank, so when the ammonia is not being redistributed, it stops the Goldfish from being able to get rid of the ammonia they produce. This then leads to ammonia poisoning.

It may also be due to where you have attained your Goldfish; if they are in a community tank, they may have been exposed to ammonia poisoning before you buy them. Therefore we recommend certain actions to take throughout this article.

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What Causes Ammonia Buildup?

To treat the problem, we first need to understand how it happens. Ammonia buildup is not unusual in a fish tank but is very easy to prevent! Goldfish are very dirty fish, meaning they create a lot of waste! This waste that’s left in the tank for a prolonged amount of time will create an ammonia buildup!

Another reason may be that you have an overstocked tank! More fish means more waste, as Goldfish primarily excrete ammonia! Or even there are rotten food remnants or certain dying or healthy plants that are contributing to the ammonia buildup.

To combat Goldfish being a dirty fish, we want to ensure that the tank is kept clean! This means that we want to do 20% water changes every 7-10 days to ensure that the tank is clean of any waste that the Goldfish produce!

With regards to an overstocked tank, the answer is very simple, research how much space your fish need and stick to it! Any uneaten, rotten food also produces ammonia! So keep this in mind when cleaning your tank.

It is also important to remember that you cannot see the amount of ammonia present in a goldfish tank. We know because we do checks, and hopefully, we catch it before it affects our pets! But do you know what you are looking for to detect symptoms of ammonia poisoning?

What Are The Symptoms Of Ammonia Poisoning?

So now we know what ammonia poisoning is and what causes it, it is important to know the signs and symptoms.

These symptoms may include:

  • Your fish may appear weak, and not move as much as it usually does or should
  • It spends a lot of time at the bottom of the tank
  • Its gills appear red or purple or may even bleed
  • The fins appear torn or damaged
  • Clamping their fins to their bodies
  • Red streaks may appear on their bodies (hemorrhaging)
  • They spend time at the top of the tank gasping for air
  • Goldfish may produce mucus
  • Their eyes may become enlarged and bulge
  • Loss of appetite
  • A general sense of disorientation

Along with these symptoms, you may notice that the water in your tank becomes cloudy, which may be a sign of ammonia due to dirt buildup.

How Do You Treat Ammonia Poisoning In Goldfish?

If your Goldfish produces any of the symptoms above, then it may be ammonia poisoning. In some cases, these symptoms can progress during a few days or even over a number of weeks. This solely depends on your fish’s immune systems and how quickly the ammonia builds up.

So how do we treat ammonia poisoning? Well, one of the first things we want to do is quarantine the Goldfish in water where the pH levels are between 7.2 – 7.8 and the temperatures remain at between 20-23 degrees celsius. This procedure will need to be done with all fish in the tank, as it is the tank that contains the disease and not the fish.

The next thing we want to do is make large quantities of water changes to the tank. You can use a treatment; however, the large water changes would be just if not more beneficial. Just ensure you do not treat the water with your Goldfish in, as it may kill them.

Once the fish are quarantined for two weeks, we need to identify the problem that is causing this buildup of ammonia. So now we need to look at the following causes.


Goldfish initially need 40 gallons of water for the first one you own and an additional 20 gallons thereafter. If you have more fish in the same amounts of water, you will continuously struggle with an ammonia buildup; as we know, Goldfish offload a lot of waste.

If this is the case, you will need to provide more tanks for your fish to redistribute how much space that they need. Keep in mind that Goldfish are social creatures, so don’t leave one on its own; in pairs, or more is best.


Overfeeding your Goldfish can be a major problem for the tank itself. If you are overfeeding your fish, there will be food residue left in the tank that is going to rot and create a very dirty environment! This will then produce high ammonia levels, which has a knock-on effect. Your Goldfish will be susceptible to ammonia poisoning if you continue to overfeed them.

(Overfeeding can also result in constipation and swim bladder disease.)


Cleaning your fish tank is fundamental for good habitat for your fish! The more we replicate nature, the better. However, in nature, if the environment is not great for them, they have the option of moving. In your tank, Goldfish do not have this luxury, so they will become more and more stressed.

Research on how to properly clean your tank before buying your fish will help, as you will be prepared to know how much work you will need to do. We provide a lot of information on the procedures you should be taking.


Unfiltered water can have its own set of problems, but while adding ammonia to the equation, the problem is tenfold. Goldfish prefer calm waters, so we cannot implement any water flow accelerators as this will only cause stress and may make the situation worse. We want to treat the water and not the fish, so filtration is important.

(Find out more about adding a filter to the tank.)


Having a thriving aquatic forest may seem like a fantastic idea as it not only looks great but gives smaller fish a place to hide if you are considering a community tank. One issue with plants is that the wrong ones can add to an ammonia problem. This is because when we look at certain plant life’s such as algae, in circumstances where they die, they exacerbate the contribution to ammonia!

How Do You Prevent Ammonia Poisoning?

Prevention is the best remedy for anything, so we want to take precautions to educate ourselves about ammonia poisoning and why it happens, rather than allowing the situation to happen and then solving it after, as you may lose your Goldfish in the process.

Let’s look at ways in which we can tackle the problem before it happens:


When you first buy a goldfish, it is important that you keep them separated from your other Goldfish. The tank you have acquired them from may have had problems with ammonia buildup, so for the first two weeks, we want to separate them to ensure they are healthy to join the community tank.

Just make sure that they are set up in their ideal environments, so you do not add any stress to the situation. We recommend that you do this with any fish you own anyway, not just Goldfish. This means that if the Goldfish develops any issues you didn’t first notice, they will not infect your tank or your other fish.


As we have stated before, accommodate the amount of water your Goldfish needs to their tank. If you cannot accommodate the amount of space a Goldfish requires, it is better for their quality of life to not own them. Goldfish need to be in pairs, so we recommend a 60-gallon tank for the first two and then an additional 20 gallons with each new introduction.

The more room you can give your Goldfish, the better, we want to encourage a regular nitrogen cycle, and because Goldfish are reputably dirty fish, more water enables this.


We now know that overfeeding means that residue may be leftover in the tank, which is not good. As much as Goldfish love to eat, there is always too much food where they are concerned. Not only do you want to ensure that your fish stay at a healthy weight, but you also don’t want them to live in cloudy disgusting water.

To negate the situation, we want to advise ourselves to use the method of ‘only feeding your Goldfish what they can consume in 5 minutes’. You may think that your Goldfish may eat it later, but chances are they will not!

If you do come across this problem, clean your tank of any leftover food, so the rotting process does not begin, and we get rid of any harm. The sooner this is done, the better; however, with the feeding method, you should mostly avoid this.


Ensuring you have a clean tank is fundamental to reducing the risk of your fish getting ammonia poisoning. For good quality water for our Goldfish we want to change the water as instructed before, whilst also removing any waste products that have built up in the substrate or ornaments/plants within your tank.

We want to ensure that we treat the water that we then add after the 20% removal and make sure it’s of the same temperature. This means we have a constant cycle of clean, habitable water for our Goldfish, and the routine checks and cleaning will keep our fish free of any disease, harm, or risks.


Although we know that Goldfish can live without a filter, it is not beneficial for them. Goldfish produce a lot of waste, so adding a filter to your Goldfish tank has many benefits.

Filters slow down the buildup of ammonia. We know that we need to do regular cleaning and checks for our fish tanks, and by not having a filter, we are speeding up the process of any spread of contaminants. We want to ensure we have a buildup of good bacteria within our goldfish tanks, and a filter is necessary for a thriving goldfish tank.


Choosing the right plants for certain fish is key to avoiding ammonia poisoning. We want to ensure that we are only putting plants in the tank that will not affect the water quality. The best live plants to complement your Goldfish tank would be Java Ferns, Anubias, Cabomba, Pennywort, or Hornwort. These particular plants will not affect the pH level or the purity of the water quality.

Is Ammonia Poisoning Fatal?

Ammonia poisoning is not good for you, Goldfish, but may not always be fatal. It really depends on how much you have let the ammonia in the tank develop.

We want to do regular ammonia testing to make sure that the water is safe. In small quantities, ammonia can create slight problems to your Goldfish, from skin tears to lethargism, which is still not what you want for your pets.

On larger scales, yes, ammonia poisoning can be fatal to your fish. If you test your water regularly, you should be able to treat it quickly. In a lot of cases, the treatment will greatly affect your Goldfish, so it’s important to quarantine them while you treat the tank and do larger water changes. 


Overall, we know that preventing and treating ammonia poisoning in Goldfish comes down to the cleanliness of your fish tank. As long as we take into consideration the amount of Goldfish we have and we are not overfeeding them, we should avoid problems with ammonia.

As we have stated, there can be other factors that may affect why ammonia builds up in your tank, but as long as you are vigilant and do the necessary preventative measures, you can overcome it quickly.

Please make sure that when you buy your Goldfish, you do subject them to quarantine from the rest of your pets, as they may have already picked up problems from their previous tanks. Taking into account this article, you should now have all the information you need to keep the ammonia exposure in your tank minimal!