Ammonia, Nitrite, Nitrate, and Chlorine are the four water parameters of interest here. Many people consider them all to be potent poisons of fish. In truth, only chlorine is a potent poison for fish. Ammonia and nitrite are only toxic at some surprisingly high levels of the toxin, dependent on pH. And nitrate is relatively non-toxic.
The many myths about ammonia, nitrite, nitrate, and chlorine are:
- Nitrates going above 10, 20, 40 or even 80 ppm will shorten the life of an adult fish.
- Long term ammonia levels at some level below 5 ppm or nitrite levels below 1 ppm at a pH of 7 decrease the life expectancy of fish because of toxicity.
- Short term ammonia levels at 5 to 10 ppm or nitrite levels at 1 ppm to 5 pm are very toxic to fish at a pH of 7 and will kill the fish rapidly.
- When a lot of fish die overnight after a water change it is typically due to ammonia, not a chlorine pulse, low oxygen or high carbon dioxide.
- The standard dose of conditioner will remove even heavy chlorine or chloramine levels.
- There are chlorine water conditioners such as Prime which “neutralize” ammonia, nitrite, and “toxins”.
- It is important to test your water frequently with test kits such as API Master test Kit, Nutrafin Test Kit, Tetra easy strips, Sera Aquatest, API 5 in 1 Test Strips, or the Fluval Water test Kit.
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All these myths are simply false.
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Toxic Levels
Acute toxicity is when the fish die in hours or days. This is the “Toxic” level in the chart below. Chronic toxicity is where the fish will have diseases and a general “failure to thrive”. This is the “Alarm” level below.
The levels are as follows:
To read the ammonia and the nitrite levels on this chart find the pH of the aquarium first. Then find that pH in the left column. Read across as to the levels the API tests will show. Green is the “Alert” level where increased testing is called for, yellow is the “Alarm” level where one should do a 50% water change. And “Toxic” is the level where one should do a 75% water change. Note many of these levels require diluting the aquarium water with 9 parts of distilled water. Test the diluted water. Multiply the results by ten and you have the levels in the aquarium.
The numbers for the toxicity of ammonia, nitrite, and nitrate will come as a shock to most experienced hobbyists. But the numbers are supported by a lot of research by universities. The ammonia levels are what Seachem delineates. They are solid. Ammonia, nitrite, and nitrate are not as toxic as we have all been led to believe. In general fish from lakes or ponds have a higher tolerance for nitrogen compounds than do fish from rivers.
Chlorine
Chlorine is toxic in very small quantities, on the order of 0.05 ppm chlorine. Chlorine is a very bad actor. The reason for this is simple. Free chlorine gas is not found in nature. Ammonia, nitrite, and nitrate are all found in nature. In the case of a lake with high organic matter, the levels of the three nitrogen compounds can get surprisingly high. So Mother Nature has provided most fish with coping mechanisms for these three naturally occurring nitrogen compounds. Nature has provided no such coping mechanism for chlorine.
Testing the Water Parameters
One constantly hears on social media the question: What are your water parameters? I.e. what are your ammonia, nitrite, and nitrate levels? And this supposedly gives one a clear picture of whatever disease the fish has. This is simply hogwash. There is simply no way to determine what disease a fish has from the water parameters.
A related myth is that it is that somehow it is important to test your water frequently with test kits such as API Master test Kit, Nutrafin Test Kit, Tetra easy strips, Sera Aquatest, API 5 in 1 Test Strips, or the Fluval Water test Kit. This makes a lot of money for a lot of manufacturers of test kits but it does little good for most aquarium hobbyists. People end up obsessing over it.
Ammonia and Nitrite Levels to Strive For
If one starts having sick fish one needs to measure the “water parameters”, namely nitrite and ammonia. The reasoning behind this is NOT because ammonia or nitrite are horribly toxic, they are not. But rather high (>0.25 ppm) nitrite and ammonia indicates the biofiltration on the aquarium is inadequate.
If the biofiltration is inadequate, dissolved organic compounds and bacterial count in the water can get high. High dissolved organics cause high bacterial count in the water. High bacterial counts in the water are one of the biggest killers of fish. So ammonia and nitrite levels become the “canary in the coalmine” for an aquarium.
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The ammonia and nitrite levels per the API tests should always be 0.25 or lower, not because ammonia or nitrite are that toxic, but rather because any ammonia or nitrite indicates poor biofiltration which will kill fish from excess bacteria in the water.
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Note all hobbyists should have aquariums with 0 ammonia and 0 nitrite after a few months of operation. The reason behind zero ammonia and zero nitrites has nothing to do with the toxicity of ammonia or nitrite. As mentioned above, it has to do with bacteria count in the water.
It has to be emphasized that achieving zero ammonia and zero nitrite takes time. An aquarium needs to be established for three or four months before this goal can be achieved, even with huge amounts of surface area in the filter. And it must be emphasized that in the meantime short excursions of up to 5 ppm ammonia, 2 ppm nitrite, and 880 ppm of nitrate or even higher for most fish will not harm the fish at a pH of 7.0.
Further Research
If one is more interested in the science and all the research papers behind all this simply read the following links:
5.1. Deleted article
5.2. Safe Ammonia Levels
5.3. Safe Nitrite Levels
5.4. Safe Nitrate Levels
5.5. Chlorine and Chloramine
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