How to lower ammonia levels in a fish tank if they are not very high

How to lower ammonia levels in a fish tank if they are not very high

Ammonia poisoning is one of the biggest killers of aquarium fish and it can often occur during the setup of a new tank. It can also occur in an established tank when too many fish are added at one time, when a filter fails due to power or mechanical failure, if bacterial colonies die off due to the use of medications, or there’s a sudden change in water conditions. Elevated ammonia can’t be seen, making regular monitoring a must so that it’s not missed. Frequent water testing can detect levels of unionized ammonia (NH3) long before it turns into the invisible fish killer.

What Is Ammonia Poisoning?

Ammonia poisoning happens when a fish tank’s ph levels become elevated, offsetting the nitrogen cycle. In ideal water conditions, ammonia levels should be nonexistent. However, tap water and the decomposition of organic matter inside the tank can both contribute to this condition.

Symptoms of Ammonia Poisoning in Fish

Ammonia poisoning can happen suddenly or over a few days. As the damage from ammonia poisoning continues, it will eventually cause damage to the brain, organs, and the central nervous system of a fish. You'll see the fish begin to hemorrhage, both internally and externally. Then, it will eventually die.


  • Gasping for breath
  • Loss of appetite
  • Lethargy
  • Red or purple gills
  • Bloody patches on the body
  • Laying at the bottom of the tank

How to lower ammonia levels in a fish tank if they are not very high

The Spruce / Alison Czinkota

Gasping for Breath

Initially, the fish might appear to be gasping at the surface for air.

Loss of Appetite and Lethargy

Your fish will start losing their appetites, as their bodily functions fail, and they will become increasingly lethargic.

Red or Purple Gills and Bloody Patches

The fish’s gills will take on a red or lilac color, making them look like it’s bleeding. As the problem progresses, the fish’s tissues will begin to deteriorate, evidenced by red streaks or bloody patches on their body and fins caused by ammonia burns.

Laying at the Bottom of the Tank

In some cases, you might find fish laying at the bottom of the tank with clamped fins. A fish with clamped fins will hold its fins folded to its body without fanning them out, and the fish will become listless.

Causes of Ammonia Poisoning

Ammonia can enter the tank in several different ways:

  • Chemically treated tap water: Some water treatment companies use a chemical called chloramine—chlorine bonded to ammonia—as a more stable disinfectant for city water systems. Using tap water that’s been treated with this chemical is a recipe for aquarium disaster.
  • Organic matter: The decomposition of organic matter—aquarium plants, fish excrement, and uneaten fish food due to overfeeding—is another way ammonia levels rise in tanks.
  • Bacteria buildup: If you do not do routine aquarium maintenance and cleaning, there will be a buildup of the bacteria that feed on this superfluous matter, resulting in an ammonia byproduct.
  • Fish byproducts: Fish, themselves, also contribute to rising ammonia levels in tanks. When a fish eats food, the protein-building process that ensues (in order for them to grow larger) can produce a byproduct that enters their blood. This results in the seepage of ammonia through their gills and into the tank.

Diagnosing Ammonia Poisoning in Fish

You will need to be on the lookout for any ammonia poisoning symptoms when setting up a new tank. One of the most obvious signs of ammonia poisoning is ammonia burns on a fish's body.


If the ammonia level in your tank rises above 1 ppm (part per million) on a standard test kit, begin treatment immediately by taking these steps:

  • Lowering the pH of the water will provide immediate relief, as will a 50 percent water change (be sure the water added is the same temperature as the aquarium). Several water changes within a short period of time may be required to drop the ammonia below 1 ppm.
  • If the fish appear to be severely distressed, use a chemical pH control product to neutralize the ammonia.
  • At this point, restrict feedings so that additional waste is reduced. In cases of very high ammonia levels, feedings need to be discontinued for several days.
  • Do not add any new fish should be added to​ the tank until both the ammonia and nitrite levels have fallen to zero.
  • If you have fish with ammonia burns, you may need to put them in a quarantine tank so they can be treated with quality antibiotic or antibacterial medication and the ammonia problem in the main tank is resolved.

Prognosis for Fish With Ammonia Poisoning

Even the smallest amount of ammonia can cause gill damage in fish and extremely high levels are oftentimes fatal. But if you can catch this problem very early in its progress and treat the water immediately, the fish can live normally. Fish treated for ammonia burns will respond to treatment within three to five days.

How to Prevent Ammonia Poisoning

Preventing ammonia poisoning involves a little bit of science to keep the water inhabitable. Start your fish off healthy when you are doing a set-up for a new tank:

Create good bacteria: When you start a new aquarium, ask a friend with a healthy, well-established aquarium for a cup of gravel from deep off the bottom of his or her aquarium. This dirty gravel is full of anaerobic bacteria that help complete the nitrogen cycle to keep both ammonia levels, nitrates, and other toxic byproducts at bay. In less than three weeks, the “good bacteria” contained in your friend’s gravel will help the nitrogen cycle complete itself in your new tank. Without this established gravel, the process takes three to four months the traditional way. Take the following steps:

I use clear, unscented, no additives, 100% pure household ammonia from the supermarket. A quart costs less than a dollar and might last you for years. You will want to place it in a container that allows dispensing by drops. An old water conditioner bottle with the right type of top is good: BE SURE TO LABEL IT! Keep it out of the reach of children. Alternatively, some aquarium stores have started to sell bottles of Ammonium Chloride for this purpose.

1. Set up the Aquarium: filters, heaters, lights and all. Be sure to dechlorinate/dechoraminate the water.

2. Place the “Ammonia Alert” in the aquarium. It usually needs a day or two to acclimate to the aquarium.

3. Keep the filter running throughout this process.

4. Provide extra aeration if possible. With an outside hang on-the-back power filter, a good way to do this is keep the water level a couple of inches lower than usual so that water falling from the filter makes a bigger splash than usual; the more bubbles breaking on the surface of the water, the more oxygen is in the water, and the bacteria need oxygen to grow. You can raise the water level when you are ready to add fish. Other types of filters may offer other aeration increasing options. Or, the addition of a simple airstone might suffice.

5. If you can, try to keep the temperature of the water up in the low to high eighties (F) for reasons explained above. Remember to adjust the temperature back down to a livable temperature for your fish before adding them.

6. Inoculate your aquarium with bacteria, either by placing some material from an established aquarium or use a commercial bacteria culture. I put a packet or two of Cycle”(TM) in the water. Wait about an hour.

9. While the ammonia level is at “safe”, test for nitrites. If it shows zero nitrites, proceed to the next step. If it does not, go back to step 8 and repeat step 8 three to four more times and then test again for nitrites.

Johnson, Erik L. July 1993. Turn Up the Heat! Tropical Fish Hobbyist XLI (11): 80-81.

Lawson, Thomas B. Fundamentals of Aquacultural Engineering. New York, NY: Chapman and Hall, 1995.

Meyer, Stephen M. November 1993. Goldfish From the Beginning, Part II. Aquarium Fish Magazine, 6(2):32-42.

In the time since this article was originally published, I’ve realized that there are some things missing from this article that would have made it a lot more useful. Also, some other experiences with the method have been reported. So here we go:

The Ammonia Alert, when used as directed, does not allow you to accurately raise the ammonia level past 0.5 ppm. However, you can calibrate your Ammonia Alert by counting the number of drops of ammonia it takes to turn it to the “toxic” level. (Unfortunately, the Ammonia Alert does not respond instantly, so this may be a somewhat tedious process.) Multiply the number of drops by two to get the number of drops it would take to achieve a 1.0 ppm level and multiply times four to get the number of drops it takes to achieve a 2.0 ppm level. Keep in mind that due to the different net volumes in different tanks, this number of drops might be different for each tank you own.

Also, the revelation that we are probably not dealing with Nitrobacter or Nitrosomonas throws some doubt on the efficacy of commercial bacterial starter cultures (Hagen Cycle, Fritz-zyme, etc.). However, it is possible that the companies involved are constantly reformulating their products or that their products are effective, whatever bacteria they happen to be using. Keep in mind that if you do choose to use one of these products, you are probably not doing much harm to the process: in view of the fish that you will not lose due to your cycling efforts, the cost of the products is minimal.


  • Beginner FAQ: The Nitrogen Cycle
  • Russell Taylor’s Cycling a Filter without Fish
  • Chow, Chris. Fishless Cycling Revisted
  •’s Fishless Cycling of The Aquarium
  • How To Establish the Nitrogen Cycle without Fish (Aqualink Column)
  • Greg Bunch’s Cycling with Household Ammonia: A Success Story.
  • Cycling Safely: The Fishless Method
  • SUIC Fisheris Bulletin 9A: Basic Principles of Biofiltration and System Design (This describes some calculations about how much ammonia to add in a fisheries situation).
  • Curt Lemricks’ Fishless Cycling gives a rationale for using Ammonium Chloride vs household ammonia.
  • Seachem’s product page for the Ammonia Alert.
  • Koivet’s Seeding a Biofilter and No More Cycle: How?

Some supplementary pages about Household Ammonia:

  • Environmental & Scientific Terms Revisited gives the pH for Household Ammonia as 12.
  • Fuming with Ammonia – Page 2 Handle with care says that household ammonia is less then 5 percent.
  • Missiippi State Extension Service Household Cleaning Products states that household ammonia is 5 to 10 percent.
  • MMWR Epidemiologic Notes and Reports Ammonia Contamination in a Milk Processing Plant states that household ammonia is 5 to 10 percent.
  • Kings County, Washington, Hazardous Waste Management Program Waste Directory – Ammonia Solution states that household ammonia is 5 to 10 percent

Meyer, Stephen M. February 1999. Cycling Fishless [Ponds and Pondfish Column] . Aquarium Fish Magazine, 11 (2):81.

Hovanec, Timothy A. March 1997. Nitrifying Bacteria [part 1] Aquarium Fish Magazine, 8 (3):44-52.

Hovanec, Timothy A. April 1997. Nitrifying Bacteria [part 2] Aquarium Fish Magazine, 8 (4):32-43.

Hovanec, Timothy A. and Edward F. DeLong. August 1996. Comparative Analysis of Nitrifying Bacteria Associated with Freshwater and Marine Aquaria. Applied and Environmental Microbiology 62(8):2888-2896.

1 Or: How to use Household Ammonia to Split an Infinitive.

2 The water chemistry definition of "alkalinity" is not, as one might assume, how basic the solution is, but how much it resists changes in pH, which is the same as its "buffering capacity".

Filtration in aquariums can be mechanical (using sponges to collect debris), chemical (to absorb specific toxins) or biological (to break down fish waste). Effective biological filtration and healthy plant growth is critical for a healthy and sustainable aquarium.

Biological filtration

To keep fish healthy and happy, a good quality biological filter is required to breakdown toxic aquarium waste products such as fish waste, food waste and decaying plants. This process is commonly referred to as the ‘nitrogen cycle’ or ‘nitrification cycle’ and refers to the establishment of beneficial bacterial colonies which break down waste products into less harmful compounds. There are three stages of the nitrogen cycle and every new aquarium must go through these three stages before biological filtration is fully functioning.

The largest contributing factor to fish loss/death in aquariums is a failure to understand this process and provide the right conditions for it to occur. In a new aquarium (or new filter) there are not enough beneficial bacteria to eliminate all toxins immediately, so for a period of two to six weeks, steps need to be taken to reduce risks to fish health and welfare and to prevent fish deaths.

The three stages of the nitrogen cycle

First stage – ammonia

  • Fish waste forms ammonia, which is highly toxic to most fish. In a new aquarium ammonia levels usually begin rising by the third day after introducing fish.

Second stage – nitrite

  • As nitrite-forming bacteria (nitrosomas) develop, ammonia is converted to nitrite and while the ammonia levels decrease, nitrite levels increase. Nitrite levels usually begin rising by the end of the first week after introducing fish.

Third stage – nitrate

  • As nitrate-forming bacteria develop (nitrobacters), nitrite levels decrease and nitrate levels increase. When nitrates are being produced and ammonia and nitrite levels are zero, your tank is fully cycled and your biological filter is fully functioning (from 2-6 weeks). In low levels, nitrates are not highly toxic to fish. Routine partial water changes of about 10% should keep nitrate levels within a safe range.

Tips for a healthy aquarium

Beneficial bacteria grow on any surface in the aquarium and they are concentrated in the filter sponge/media which has a high surface area. By constantly flowing water through the filter, ammonia and nitrite are rapidly converted to nitrates, assisting in keeping tank water free of toxic levels of these compounds. You should avoid completely cleaning a tank as this will remove the beneficial bacteria. Instead, partial water changes of approximately 10% should be performed once per week, using a gravel vacuum to remove waste and uneaten food from the substrate. At this time the sides of the tank can be wiped with an aquarium safe sponge and filter media and/or decorations can be cleaned in old tank water.

Regularly test your water for ammonia, nitrite & nitrate levels to ensure your biological filtration is sufficient, you are maintaining it appropriately and your aquarium is not overstocked or overfed.

Your filter is ultimately only as effective as the media it contains. There are many types of biological media available on the market and it is important to select a media which has a high biological capacity.

Do not add large numbers of fish to your aquarium at any one time – gradual introduction will enable the filtration bacteria to slowly adapt.

Please note that in marine/saltwater aquariums fishless cycling and using live rock to cycle the aquarium is often recommended.

Further information is available from the following website:

If you need specific advice on how to safely cycle a tank, please consult an experienced aquarist or fish veterinarian for further advice about how to safely cycle a tank.

Any time an aquarist adds any type of organic matter (including live animals and live rock), ammonia will result.

It is normal to see the ammonia level rise during the cycling period of a new aquarium. Do not try to lower the ammonia if you are cycling a new tank by using ammonia remover; you are only preventing the cycling process from taking place. Using a product such as FritzZyme® or TurboStart® will help lower the ammonia without disrupting the cycle of the aquarium.

Ammonia occurs in two states depending on the pH of the water. The unionized state, NH3, is more toxic than the ionized state, NH3+4. The unionized state can invade the body tissue of marine animals much easier. Almost all free ammonia in seawater with a normal pH is in the ionized state, thus less toxic. As pH rises, the less toxic ionized state decreases and the more toxic unionized state increases. For example, a toxic level of ammonia as NH3 may be present with a pH of 8.4 being lethal, but the same level of ammonia as NH3+4 with a pH of 7.8 may be tolerated. Higher tank temperatures can also affect the toxicity of ammonia.

Testing for ammonia is extremely important. Ammonia will be elevated during a new tank cycle but can also be elevated in established aquariums if the aquarium is not maintained. If water is not changed regularly, filters are not kept clean, the tank is overstocked, or medication is used that disrupts the biological cycle, ammonia levels can increase. Test immediately any time you have sick fish or a fish death. Ammonia is measured at parts per million (ppm). Aquarium water quality is critical to the health of tank inhabitants. Lethal levels of ammonia can accumulate very rapidly in the absence of true nitrifying bacteria. The ideal ammonia reading should register at “0.”

Best level Information and References website . Search all about level Ideas in this website.

How To Check Ammonia Levels In Fish Tank Without Kit. While nitrates might not be as deadly as ammonia, you still want to keep levels low in your tank. Continue to change the water daily until the ammonia nitrate drops to a safe level.

Top 10 Best Freshwater Test Kit (2022) Fitnessequipment from

How do you lower ammonia levels in a fish tank quickly? Without a test kit, you can estimate the condition of the growing nitrogen cycle by carefully observing the fish and the water. So rather than waste your time with the science behind it, here are 10 things you should do right away if you have an ammonia spike in your tank.

Top 10 Best Freshwater Test Kit (2022) Fitnessequipment

[ 1] if ammonia levels are higher than zero, you need to find the cause of the problem, and fast. Ensure your filter isn’t clogged and it is flowing freely. If it smells normal than you are good but if it has a smell than either your ammonia or nitrite is high. Continue to change the water daily until the ammonia nitrate drops to a safe level.

Cxv/s-l1600.jpg” alt=”Ammonia Max 55 OFF Test Kit for fish salt or water pond” />Potentially reduce the amount of food you are offering. Ad compare prices & read customer reviews. Continue to change the water daily until the ammonia nitrate drops to a safe level. Look for any dead fish. How do you lower ammonia levels in a fish tank quickly?

Cx7/s-l1600.jpg” alt=”Ammonia Max 55 OFF Test Kit for fish salt or water pond” />Potentially reduce the amount of food you are offering. In a stocked tank, your aquarium test kit reading for ammonia should read 0 ppm (parts per million). Run an ammonia reducing product in your aquarium for at least two weeks or until you see zero ammonia on the test kit. How to fix high ammonia in fish tank. So rather.

You will need to test the water for ammonia levels. The water may look clear and clean, yet still have high ammonia levels.Test kits are commercially available or your fish veterinarian can test the water for you. Always bring a separate container with a sample of your fishes’ tank/aquarium water to the veterinary consultation to submit for ammonia testing.

Increased mucous production

Red or bleeding gills

Body colour darkens

Increased respiration rates and fish seem to “gasp” air at the surface of the water

Regular water changes (25-50%) to dilute the ammonia levels in the water.

Add chemical filtration

activated charcoal (for freshwater or marine tanks)

zeolite (for freshwater tanks).

Add commercial chemicals (e.g. ammo-lock)

These chemicals bind up the toxic ammonia(NH3) and change it to non-toxic ammonium (NH4+).

Note:any further ammonia tests will have a high result despite the ammonia now being temporarily non-toxic.

Add 1-2g/L salt to the water to relieve the stress on the kidneys of the fish.

Increase the oxygenation of the water by the addition of air stones to lower the chance of suffocation.

Decrease or stop feeding fish during a crisis as this will lower the amount of ammonia added to the water.

Decrease the number of fish in the tank.

Correct the temperature and pH over a few days to one week.

Antibiotics and other medications may be prescribed for secondary infections.

How to lower ammonia levels in a fish tank if they are not very high

Ammonia can be a real danger to your fish, as Matt Clarke explains.

What is ammonia?

Ammonia (NH3) is the most toxic nitrogenous waste found in the aquarium and is capable of quickly killing fish, or causing them to become diseased. It’s produced in the breakdown of organic materials, and by the fish themselves as a by-product of their metabolism. In fact, the vast majority of ammonia is excreted from the gills of your fish.

Why is it dangerous to my fish?

Ammonia affects the gills and blood of fish and the fish produce extra body and gill mucus to relieve the burns it causes. Extra mucus covers the gills, and reduces the ability of the fish to absorb oxygen.

Ammonia is also directly toxic, and may reduce the ability of the haemoglobin in the fishes’ blood to retain oxygen.

How is it normally broken down?

Under normal circumstances, when the biological filtration is mature and functioning correctly, beneficial bacteria in the filter will utilise ammonia as an energy source and turn it into nitrite. Other bacteria then use the nitrite and churn out nitrate, which you need to remove by changing some of the water each week and topping up with dechlorinated tapwater.

What are the symptoms of ammonia poisoning?

Since ammonia tends to affect the gills first, gasping is one of the first things you’ll notice. Fish may gasp at the surface where the oxygen level is greatest, or lay on the bottom, conserving energy but breathing heavily.

You may also see them holding their fins tight against the body, scratching against objects in the tank, or if you spot the problem late, you may notice that they have succumbed to disease.

How do I know if ammonia is present?

The only way you can detect ammonia is to use a proper test kit. Get into the habit of testing your water weekly for ammonia, nitrite, nitrate and pH, and check again if your fish look unwell or are acting unusually. A single ammonia test kit can cost as little as 5-10, but you can buy a master kit covering the four most important ones for 15-20.

What causes the ammonia level to rise?

There are lots of different reasons why ammonia levels might rise. Here are some of the most common things you need to investigate if you detect ammonia in your test results.

  • New tank with insufficient bacteria.
  • Filter has been washed in tapwater or an old sponge has been replaced.
  • Disease treatments have killed the filter bacteria.
  • Overfeeding.
  • Overstocking.
  • Insufficient filtration.
  • Tapwater has not been treated correctly (chlorine or chloramine).
  • Too many fish added too soon.
  • Dead fish decomposing in the tank.
  • Uncured living rock.

What is ammonium?

Ammonium, NH4, is a less toxic form of ammonia. When ammonia is present in your water, some of it will be deadly free ammonia, NH3, and some of it will be less toxic ammonium, NH4. The amount of each present depends on the pH and temperature of the water.

How do I interpret my ammonia test results?

Bizarrely, most of the test kit manufacturers omit some vital details from their test kit instructions, presumably to make things a little less confusing for the tester. For a start, all aquarium test kits measure the presence of something called Total Ammonia Nitrogen (TAN) and not solely ammonia, as you might think.

Total Ammonia Nitrogen is made up of ammonia and ammonium, and the proportion of each that is present in your water will depend on its temperature and its pH. To find the real ammonia level you need to use a special look up table, which again isn’t provided with most test kits, and compare the pH, temperature and TAN level to the figures on the chart.

What is a safe level for ammonia?

There’s no “safe” level, as the presence of any ammonia is cause for concern. You ought to try and find out why ammonia is present as soon as you find it, and then take measures to remove or dilute it as quickly as you can.

What should I do if I detect ammonia in my water?

How you tackle the problem depends on the cause. You may have to do a bit of detective work to find out what you’ve done wrong. But first undertake an immediate large water change. Make sure the new water is dechlorinated and of the same chemistry and temperature.

If ammonia continues to increase, monitor the tank closely with your test kits and do additional water changes to keep the levels low.

Nitrite levels may also rise following an ammonia problem, so be ready to dose your aquarium or pond with salt (at about 1-3g per litre) to reduce its toxicity to your fish.

It helps considerably if you can add something to the water, or the filter to remove or neutralise ammonia.

How do I make ammonia less toxic?

The quickest thing to do is to conduct a large partial water change and top up with dechlorinated water. A lot of people might tell you that you should be careful not to change too much water when you do this, advising perhaps just 35%, to avoid upsetting the fish. My personal opinion is to ignore this. If ammonia is present at a toxic level you need to get rid of it fast. I wouldn’t have any concerns about changing 50% or more of the water to sort the problem out temporarily.

What is zeolite and why might it help me?

Zeolite is a natural crystalline mineral (hydrated aluminosilicate), formed millions of years ago when volcanic ashes were deposited on the floors of alkaline lakes.

The one we use, clinoptilolite, is one of over 40 different zeolites. It can remove certain ions from the water, such as ammonium, phosphate and calcium, via two processes: adsorption and ion exchange.

In ion exchange, ammonium and other ions are taken in and exchanged for sodium from the zeolite, and locked away safely. When it’s full, you remove it from the tank or pond and soak it in saltwater. Ammonium and other ions are swapped back for the sodium in the salt, and after a rinse it’s used again.

It also removes the same ions by adsorption, but this can result in some of the ions, including ammonium, being released back into the water at a later date. So zeolite won’t last forever and can only be recharged and remain effective so many times.

It’s an effective solution in emergency ammonia situations, but keep testing and making water changes, because it’s not removing the free ammonia, just the ammonium. You may need to recharge it daily, so buy two bags and recharge alternatively.

It’s less effective with increasing pH and hardness, and won’t work in water that contains salt. Bulk zeolite for pond use can be picked up very cheaply, often for as little as 10-15 for 10 l.

This article is from the Practical Fishkeeping website archives.

Old tank syndrome occurs in fish aquariums with high levels of ammonia and nitrite and low levels of water pH. It can be caused by overstocking, but is most commonly the result of inattentive tank maintenance. This condition can affect an age or species of fish, but is most dangerous to new fish that are added to established aquariums.


The primary symptom of old tank syndrome is the death of new fish that are placed into a long established tank, while the old fish remain alive and apparently healthy. This is because the old fish are accustomed to the balance of the water, even adjusting to conditions such as build-ups of certain chemical or bacterial levels. The old fish often do not show any signs of being affected by the unhealthy levels in the water. The new fish, however, have been accustomed to a different water balance and are shocked by the sudden change in conditions.

On testing, the water will show measurable nitrite and ammonia levels, which can be toxic to fish, and a lowered pH level. pH levels below 6 indicates a serious imbalance, often leading to the loss of beneficial bacteria, which then leads to a dangerous and toxic increase in ammonia and nitrite levels in the water.


The cause of the high levels of ammonia — which leads to old tank syndrome — is often due to less than ideal water maintenance, and a sudden drop in the water’s pH level. When the pH of the water suddenly drops below 6.0, the biofiltration system is unable to metabolize ammonia properly. This can also potentially occur when new water is added to a tank in excessive quantities.


If your fish are suffering from old tank syndrome, begin by adding a few gallons of new water each day. This will allow the water to adjust to healthy bacterial levels again, and the fish to adjust to the change gradually. Remember that your old fish have become accustomed to the levels in the water, even though the levels are unhealthy. Too much of a change to very clean water may kill your fish.

Once the beneficial bacteria are well established again, ammonia and nitrate levels will drop back down to levels closer to zero — as they should be. Never dump the water entirely and start with new water and materials, as this could result in “new tank syndrome,” a toxic condition that can result in the deaths of all of your fish.


To prevent old tank syndrome, maintenance is the primary concern. New water should be added to the old on a regular basis to maintain acceptable pH levels. Never remove and replace the water entirely, as that could cause another set of problems. Additionally, testing the water balance is an essential part of caring for fish. Performing regular pH tests on the water will enable you to monitor and track the health of your fish water and make adjustments accordingly.

Ammonia levels greater than 2 mg per liter will cause toxicity symptoms in the fish.

Ammonia poisoning is a very real threat to your fish, especially when the tank is new and is still cycling or if the tank has been stressed and the biological filter has been upset or removed.

Ammonia stress is caused by two occurrences in the aquarium chemistry. First is the build up of toxic ammonia and nitrite in the water. This directly affects the fish and can have a number of harmful side effects – from increased disease susceptibility to organ failure. The second component of ammonia stress is the displacement of oxygen in the water by the ammonia. The more ammonia is in the water, the less oxygen is available to your fish and your biological filter. Not only does this further stress the fish and pose a risk of suffocation, but it also decreases the efficiency of the biological filter. This is among the reasons that water changes are so important when your tank is cycling to insure a smooth and headache free cycle.

What is the Difference Between Ammonia Poisoning and Ammonia Stress?

Ammonia stress and ammonia poisoning are really the same thing. It is also referred to as nitrogen poisoning or nitrogen stress as well. Generally, though it is not referred to as ‘poisoning’ until you have actually lost a fish. Until that time, it is referred to as ammonia stress.

Signs of Ammonia stress

The signs of ammonia stress are usually pretty easy to detect, especially if you are paying attention to your fish regularly.

  • Lethargy
  • Loss of appetite
  • Hovering at the bottom of the tank (especially for surface dwelling fish)
  • Gasping at the surface
  • Inflamed gills
  • Red streaks or inflammation in the fins
  • Inflamed eyes or anus

This list of symptoms is by no means exhaustive of the symptoms of ammonia poisoning or ammonia stress. However, these are many of the more common symptoms, and generally they will show up in more-or-less this order. However, since, especially in new or particularly small tanks, the ammonia level can rise quite quickly, particularly if the tank is overpopulated, you may see a very rapid succession between these symptoms.

What Do I Do for Ammonia Stress or Ammonia Poisoning?

Actually, this is quite simple – do a water change. You may be tempted to use an ammonia remover, however, this should almost always be avoided because this can have long-term negative side effects on the tank, and is rarely helpful for very long.

A water change, however, will remove some of the excess ammonia from the aquarium (provided you are not using source water with a lot of ammonia in it), and will allow the biological filter to begin to process the excess waste while relieving the stress on the fish.

when the tank is still cycling, you will need to perform these water changes regularly to keep the ammonia from building up and prevent ‘new tank syndrome,’ which is usually just ammonia poisoning.

What if Ammonia Poisoning Keeps Coming Back?

Once the tank has cycled, you should no longer be seeing signs of ammonia stress or ammonia poisoning. If you are seeing similar stress symptoms, there could be another chemical problem with your water, or your fish may be sick.

However, if the ammonia poisoning keeps coming back, you may have another problem. The most common is overpopulation, though over feeding can also be a cause of ammonia poisoning. Insufficient filtration can be another contributor to high ammonia levels in the fish tank. If you repeatedly run into ammonia problems, provided the tank is cycled, you should look first into your tank population, then at your feeding habits, and then into your filter maintenance, tank cleaning, chemical use, and the overall capabilities of your filter.

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        Good water quality within any aquarium is essential to the long-term health of all aquatic species. Poor water quality is the main factor leading to poor health, disease and even fish death. The only way to determine water quality is through accurate testing. Following feeding, ammonia is produced from the waste of fish and invertebrates, most of the excreted nitrogen is in the form of ammonia released directly from the fish through their gills. Even at relatively low concentration, ammonia within an aquatic environment is highly toxic and may cause gill damage, skin irritation and sometimes death. Therefore, the testing of ammonia levels within a tank is essential.

        Physical signs of fish with acute ammonia poisoning include damaged gills, clamped fins, unusual darkened areas on the body, gasping at the surface, and cellular damage often seen as ragged fins. If left unattended the fish will slowly become lethargic and either succumb to disease or inability to osmoregulate.

        Ammonia exists in two forms, namely, unionized (NH3) and ionized (NH4+). Both forms are measured together and are referred to as total ammonia nitrogen (TAN). Most ammonia test kits are actually testing TAN (Total Ammonia Nitrogen). TAN is a combination of unionized ammonia (NH3) and ionized ammonium (NH4+). Ammonia (NH3) is a highly toxic chemical to fish and changes from ammonia to ammonium and back again relative to the pH level and temperature. API Ammonia Test Kits, both Liquid and Dip Strip, test for TAN. To calculate the unionized ammonia (NH3) from TAN you can use the table at the end of this article. However, when ammonia is present even in trace amounts your fish are being damaged. Regular testing and taking corrective action immediately are advised to protect your fish. Once fish have started to die from ammonia poisoning it is very difficult to make corrections without further loss of fish. When testing your aquarium water, the only safe level for ammonia is zero.

        Unlike nature, an aquarium is a closed environment, where all the ammonia and ammonium from the wastes excreted from the fish, uneaten food, and decaying plants stays inside the aquarium. Fish feces and urine, as well as any uneaten food, are quickly broken down into either ionized or unionized ammonia. The ionized form, Ammonium (NH4+) is predominant if the pH is below 7 and is relatively non-toxic to fish. The unionized form, Ammonia (NH3), is predominant if the pH is 7 or above, and is highly toxic to fish. The problem is that slight changes in pH can take an environment of low toxicity to high toxicity. Remember, even low toxic conditions or slight toxic conditions cause damage to fish and lower the immune systems of fish. Even at low levels, ammonia problems are documented in reduced growth and damage to gill filament tissue. The lethal effects of exposure to ammonia are severe gill damage leading to suffocation, kidney damage due to inability to osmoregulate, and the increased inability to secrete ammonia from the body resulting in metabolic and physiological imbalance. Temperature also plays an important part along with pH in the toxicity level of ammonia.

        A lethal poisoning level for the unionized (NH3) form is 1.00mg/l; a sub-lethal level is 0.05mg/l (Noga, E.J., (1996) Fish Disease, diagnosis and treatment. p 62-66.). The toxicity of ammonia is dependent on the water pH, and temperature since an increase in pH and temperature both favor the conversion of NH4 to NH3. The percentage concentration of NH3 in water can be determined from a standards chart (Appendix 1).

        The levels of ammonia are reduced by biological filtration and in a closed system, such as the aquarium, should be zero. The biological filtration houses beneficial nitrifying bacteria to break-down ammonia produced by fish to nitrite and then nitrites are converted to nitrates. This is commonly called the “Nitrogen Cycle”, see diagram above. The design of the system, limiting the fish load to a realistic carry capacity based on testing, and a suitable feeding regimen are the best ways to control ammonia.

        In conclusion, attempting to educate the average hobbyist on the use of the chart below is problematic at best. It provides a false sense of safety when they think that ammonium is not harmful, which is not true. Ammonium and ammonia are released from the fish, mostly from their gills (85% and up), the remaining accumulation of ammonia and ammonium in the aquarium come from feces, urine, uneaten fish food and other amine organics. If the ammonia or the ammonium is high in the aquarium it is harder for the fish to release either of these compounds from their blood. This can cause the ammonia/ammonium levels in the fish to be higher than the surrounding aquarium water being tested.

        The only safe TAN (Total Ammonia Nitrogen) level for an aquarium is zero. API AMMONIA TEST KIT provides the answer for the TAN (total ammonia nitrogen) in a responsible way for all hobbyists to easily understand and, most importantly, to protect their fish!