All About Ammonia and Trout

Excess ammonia causes many problems in fish. One significant effect is damage to the gills. Although the most obvious consequence of this is impaired respiration (breathing) this isn't the only problem. Gills are also important for acid-base balance (keeping the pH of the fish's blood correct to allow for normal processes to occur) and ion exchange (keeping the correct amount of important ions such as sodium and chloride in the blood). Thus, damage to the gills prevents a number of important processes from occurring. This leads to extra stresses on the fish as well as an increased potential for infection by bacteria and other invaders.

Ammonia also causes damage to skin, fins and the intestine. More chronic ammonia exposure can cause kidney damage, decreased growth and overall immune suppression. Ammonia also affects the nervous system, resulting in erratic swimming behavior.

What to watch for:

•  gasping/ impaired respiration 

•  abnormal swimming/whirling

•  bloody areas on the body

•  increased mucus production

•  bloody areas in the intestine

•  acute death

What causes excess ammonia?

•  overfeeding 

•  excess leftover food in tank

•  decaying food or animal matter trapped in filter

•  die-off of healthy  bacteria colony due to something like chlorine

•  a tank that was not properly cycled yet and lacks the healthy bacteria needed for the nitrogen cycle

How to decrease ammonia levels in a tank:

•  20% water change two to three times a week (siphon from the bottom of the tank) 

•  make sure you are not overfeeding

•  clean decaying food or animal matter trapped in filter and in gravel

•  add ammonia chips to filter (use only for a temporary emergency fix)

•  use a water conditioner such as Amquel

Thanks to Chuck Dinkel, co-coordinator of the Maryland TIC program, and Lilli Genovesi, NY TIC Coordinator, for this information.

More on  Ammonia – pH – Water Temperature 

by Chuck Dinkel, MD TIC

When raising fish there is nothing worse than seeing your fish suddenly die without any apparent reason. Teachers sometimes remark that their perfectly good fish that were fine yesterday suddenly looked sick and died this morning.

One point that many people overlook in fish culture is the relationship between ammonia levels, water temperature and pH. If neglected or not understood their inter-relationships can lead to fish mortality


All fish give off ammonia. It comes off their gills and waste. Uneaten fish food turns into ammonia as it breaks down. If left to build up over time without nitrifying bacteria to convert it into nitrites and nitrates it will cripple your system and kill your fish. This is known as the Nitrogen Cycle. At the water temperatures we raise trout it can take six to eight weeks for a tank to fully cycle

Ammonia concentration in a new aquarium is a chemical that has to be watched closely to make sure the levels do not reach a point where they start killing fish. The death of many species of fish can start at as low as .6 parts per million (ppm). In established systems the ammonia level normally reads 0 ppm. When you test for ammonia with your aquarium test kit, the reading you actually have is a combination of ammonium (NH4+ or ionized ammonia) and ammonia (NH3 or unionized ammonia) known as Total Ammonia Nitrogen (TAN). Ammonia is the toxic part of the TAN. Ammonium even at high concentrations does not cause mortality in fish. Understanding the difference between the two is crucial to figuring out how much toxic ammonia you really have in your system. How much of the TAN you have that is toxic is greatly related to the pH of the water, and to a much lesser extent the temperature. The higher the pH the greater amount of the TAN is ammonia. Water with a temperature of 82° F (28° C), a pH of 7.0, and a TAN of 5 ppm has only .03 ppm ammonia. . At a pH of 6.0, and 10 ppm of TAN, the ammonia is only .007 ppm. Above a pH of 8.0 the toxicity of TAN rapidly rises!

The pH of Ammonia

Pure ammonia actually has a basic or alkaline pH. In theory, ammonia should raise the pH of an aquarium. However, virtually all processes in the aquarium that produce ammonia, as well as the breakdown of ammonia, produce hydrogen cations. Since pH is the negative log of hydrogen cation concentration, increasing this lowers the pH, negating the mildly basic pH of ammonia. While ammonia has a basic pH, the processes that create it in an aquarium produce enough hydrogen ions to overcome this and lower the pH.

Sources of Ammonia

Ammonia comes from several biological processes in the aquarium. Most of these processes come down to breaking down proteins. In a fish's metabolism, they break down proteins from the food they eat and produce toxic ammonia as a byproduct. This releases ammonia, and hydrogen ions. Since ammonia is a weak base, the hydrogen ions have a stronger effect on pH, so this process ultimately lowers the pH. Rotting plant and animal matter, as well decaying fish food, also undergo a similar process that produces ammonia and hydrogen ions.

The Ammonia Cycle

In a healthy aquarium, bacteria break ammonia down into less toxic forms. A first set of bacteria break ammonia down into nitrite. A second group of bacteria turn the nitrite into nitrate. The various bacteria also release even more hydrogen ions throughout this process which lowers pH. The process typically takes several weeks to a month to establish in new aquariums. Without this process, toxic ammonia would continue to build up until the water became toxic to fish.

How pH Effects Ammonia

While the processes that create ammonia affect pH, the aquarium's pH can also influence the ammonia. In an acidic aquarium, ammonia actually becomes less toxic to fish. It is never good to have ammonia in an aquarium, but it is "less bad" in an acidic situation. In water with alkaline or basic pH, ammonia is more toxic.  

How Temperature and pH Effect Ammonia

Ammonia varies in toxicity at different pH and temperature of the water. For example, ammonia (NH3) continually changes to ammonium (NH4+) and vice versa, with the relative concentrations of each depending on the water's temperature and pH.. At higher temperatures and higher pH, more of the nitrogen is in the toxic ammonia form than at lower pH.

At what point should you get concerned about ammonia levels becoming a threat to your fish given that ammonia is constantly being produced? The answer to this question will depend on the temperature and pH of your tank water, how many fish are in your tank and how much uneaten fish food remains in the system.

This chart identifies the level of ammonia you can tolerate in your fish tank before it affects the fish. You will notice that at very warm water temperatures a small amount of ammonia can be toxic to your fish. At the opposite end of the spectrum in very cold water, the opposite is true. Fish can tolerate higher levels of ammonia the cooler the water. This is also true for dissolved oxygen. Cold water can store more dissolved oxygen than the same volume of warm water. The good news is that the water temperatures and pH levels at which our trout are raised tend to reduce the effect of harmful ammonia. If you encounter an ammonia spike that is causing fish mortality you may try lowering the water temperature 2-4 degrees to see if the fish start to recover.

Understanding the relationship between ammonia, pH and water temperature will help you control and manage your system and avert fish loss.

Note: The Total Ammonia Nitrogen table is printed by permission of Frank Gapinski of Eco Films, an independent production house based in Queensland’s Sunshine Coast, Australia. Ph: 07 54749893 email inquiries:

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