Aquarium Ammonia Spike 101: Causes, Signs, Solutions & More

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If you’ve measured ammonia levels of 0.25 ppm or higher, you have an ammonia spike in your tank. This is a pretty common thing that many fish owners have to deal with at some point.

While some fish can tolerate an ammonia spike, in the long haul, it is dangerous. Even the most resistible creatures may die if you don’t take the proper measures.

In this article, I will discuss what causes an ammonia spike, how long it typically takes for this to happen, and what signs are associated with this issue. Then, I will list some practical steps you can take to overcome the situation quickly.

Still curious? Feel free to check my complete guide on aquarium ammonia, where I discussed what causes ammonia, how to get rid of it, what equipment to use, and much more.

What Would Cause An Ammonia Spike In Aquariums?

NH3 is the toxic aspect of ammonia, and a spike in NH3 can kill your fish. Unfortunately, ammonia can spike for any number of reasons, including:

1. Large Fish Populations

Fish excrete ammonia through their gills, but they are not unique in that arena. Higher vertebrates will also eject ammonia as nitrogenous waste.[1]

But the amount of ammonia a fish excretes is not exceptionally high. This phenomenon only becomes a challenge when you overwhelm your tank with fish.

Large populations of fish in a small aquarium are more likely to chock the water with ammonia.

2. Fish Waste

When fish consume food, waste is a natural byproduct. But if you allow the waste to linger in the water, it will produce ammonia when it breaks down.

If ammonia levels in your tank have spiked unexpectedly, you probably have large quantities of decomposing waste. 

3. Uneaten Food

Uneaten food is just as bad as fish waste. Leftovers produce ammonia when they decompose.[2]

Therefore, the ammonia concentration will spike if you permit large quantities of leftovers to sit in the water.

Uneaten food is one of the most common reasons for an ammonia spike as it is difficult to remove it from the substrate.

4. Tap Water

If you get your water from a tap, you probably apply de-chlorinators to the new water whenever you perform a water change. 

Conventional de-chlorinators are perfectly fine if the authorities in your area use chlorine to purify the water. But if they prefer chloramine, the de-chlorinator will remove the chlorine and leave the ammonia behind.

In other words, ammonia will spike whenever you perform a water change because the new water is a potent source of ammonia.

Many aquarists fall prey to this trap because they don’t realize that chloramine is a combination of chlorine and ammonia.

5. Inappropriate Cycling

If your tank isn’t cycled, ammonia will repeatedly spike despite your attempts to clean the tank because the nitrifying bacteria aquariums use to process ammonia is absent.

In healthy tanks, there are bacteria responsible for turning ammonia into nitrite via the nitrogen cycle. The process of growing that bacteria in new tanks is called cycling.

How Long Does It Take For Ammonia To Spike In Aquariums?

It depends on the conditions. The cycling process can take anywhere between two and six weeks.[3] During that time, the ammonia concentration will rise.

If you added fish waste and leftovers, it might take a week for these items to produce sufficient ammonia after decomposing.

Over time, ammonia levels will fall as your colony of nitrifying bacteria enters the picture. However, an aquarium can manifest detectable ammonia levels within 24 hours.

What Are The Signs of An Ammonia Spike In Fish Tanks?

Ammonia is dangerous. Fortunately, it is relatively easy to spot. The following signs will accompany an ammonia spike:

1. Cloudy Water

New tanks are often cloudy because the ammonia concentration has to rise before the nitrogen cycle can start.[4] Cloudy water in a new tank is not a problem.

However, cloudy water in an established tank with fish should concern you because it signifies high ammonia levels.

A discus fish swimming in cloudy water, secondary to high ammonia levels.

2. Erratic Swimming

The fish will start swimming erratically because ammonia is toxic, and they want to escape the water. But they have nowhere to go. 

As such, they will dart about randomly, occasionally colliding with the plants, decorations, and walls.

3. Lethargic Fish

Over time, the erratic swimming will fade, and the fish will either settle at the bottom or swim sluggishly through the water. They may become inactive altogether.

Fish exposed to high ammonia levels will also be less interested in food. This will also contribute to their lack of energy. 

4. Gasping For Air

An ammonia spike will send some fish to the surface, where they will gasp for air. This is because ammonia burns the gills, compromising the fish’s breathing ability.

Some aquarists will blame gasping on an oxygen deficiency. But if your tests have revealed sufficient oxygen in the aquarium, check the ammonia levels. Better yet, look at the gills. 

5. Ammonia Burns

Persistently high ammonia levels will produce chemical burns along the fish’s skin. In some cases, the burns are so intense that the fish looks like it is bleeding.

Ammonia burns are nothing to scoff at. They can kill the fish, especially if the creature contracts bacterial infections.[5]

This goldfish is suffering from ammonia burns that look like bleeding.

How Long Does An Ammonia Spike Last?

In a cycling tank, the ammonia concentration will rise in the first stage. Once nitrifying bacteria appear in the water, they will turn the ammonia into nitrite. During this process, you’ll be required to add ammonia to feed the bacteria.

As the nitrite levels rise, the ammonia concentration will fall. It can take up to six weeks for the ammonia levels to fall to 0ppm.

In an established tank, you can remove ammonia by applying water conditioners. Some conditioners neutralize the ammonia within minutes. With others, it may take 24 hours for the ammonia to fall to undetectable levels. 

How Do You Fix An Ammonia Spike In A Fish Tank?

Ammonia is dangerous. Therefore, you must act quickly to protect your fish:

1. Making A Large Water Change

Start by performing a 50 percent water change. Don’t forget to condition the new water. Check with your supplier. Identify the chemicals they use to purify the water. 

If the water has chloramine, use conditioners that eliminate chlorine and neutralize the ammonia. You can also look for alternative water sources, but you should test them beforehand. 

Ammonia is not the only threat to your fish. In an attempt to avoid ammonia, you may introduce toxins like lead. Some aquarists will pair water changes with aquarium salt to aid in the recovery of the fish.

2. Cycling The Tank Properly

If you suspect that your tank is not cycled, move the fish to a separate aquarium and cycle their old home to completion. That will stop ammonia from building up in the future.

If you cannot afford to wait the six weeks it usually takes to introduce nitrifying bacteria, expedite the process by adding biofilter media and gravel from an established aquarium.

You can also use products like API Quick Start Nitrifying Bacteria (link to Amazon). This product contains premade bacteria that take a while to build up naturally.

I also suggest using this product when adding new fish to your tank, making a significant water change, changing the filter media, or when ammonia or nitrite are detected.

3. Consider A Larger Tank Size

The quantity of nitrogen fish excrete is small.[6] But ammonia can still rise to dangerous levels if you have too many fish. This leaves you with two options. 

You can either increase the tank size or reduce the number of fish. If you don’t have the money to buy a bigger aquarium, it makes more sense to donate some of your fish.

4. Remove Fish Waste

Vacuum the substrate to remove waste and leftovers. You should also invest in a suitable filter. Filters and vacuums work hand in hand with water changes to keep the aquarium clean.

You should also pay close attention to the quantity of food you add to the water. Overfeeding increases the volume of waste and leftovers. 

I personally recommend getting the Laifoo Aquarium Siphon Vacuum Cleaner (link to Amazon). This cleaner is pretty affordable and gets the job done. 

If you’ve never vacuumed the substrate before, here is an excellent Youtube video that will show you how to do that properly:

5. Use A Water Conditioner

As I previously explained, water conditioners don’t remove ammonia. Instead, they bind to the toxin and neutralize it. In other words, ammonia remains in the aquarium in its non-toxic form.

What you should also look for in a water conditioner is its capacity to bind to chlorine and neutralize it. That is crucial as chlorine and ammonia can bind and form chloramine, which is challenging to eliminate.

I personally use the well-known Seachem Prime Conditioner (link to Amazon). This product will work in both directions. It will get rid of chlorine and neutralize the ammonia.

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If ammonia has spiked in your tank, you should first perform a significant water change, up to 50 percent. Water conditioners are also worth considering as some detoxify ammonia quickly.

Then, check for decaying matters, such as rotten food and dead organisms. Vacuuming the substrate is one of the best solutions to this problem. You won’t believe how many particles are hidden down there.