Ammonia in the Freshwater Aquarium
by: Lou Tranchitella

Who cares about ammonia? You should, if you keep an aquarium. Ammonia is a main component in the biological processes that occur in your aquarium. Once your tank has cycled, ammonia should not be an issue in your tank. If the normal biological processes are disrupted however, you could face an ammonia spike which could be harmful to your aquatic inhabitants. This article will discuss some of the chemistry involved regarding ammonia in an aquarium.

Ammonia is constantly being produced by fish as a by-product of their natural metabolic processes. The main source of ammonia production comes from the deamination of amino acids in the liver. Deamination occurs when proteins and amino acids are broken down to be used as an energy source, much like carbohydrates (sugars and starches) often are. The remaining carbon skeletons are then used, by a series of linked cycles, to facilitate the harvesting of energy derived from oxygen in the process of respiration. This process also occurs to a lesser extent in the kidneys, muscles and intestines. Ammonia is excreted by fish mainly through the gills (as ammonium ions, a less harmful form of ammonia) and is also released to a much smaller extent in their urine. Ammonia can also be produced from the breakdown of uneaten food or other decaying organic matter (a deceased fish, dead plants etc.).

In a properly cycled tank, there are nitrifying bacteria present that converts ammonia to nitrites and nitrites to nitrates. If the cycle of your tank is disrupted or broken (or the nitrifying bacteria are depleted or killed off), the build up of ammonia from normal fish excretion can happen in a matter of hours. This can sometimes happen during a power loss, when the filter is off for a period of time. Remember, one function of a filter is to provide water movement and surface agitation which enhances oxygen exchange. Oxygen is not only necessary for your fish, but also for the bacteria which consume ammonia and nitrites, eventually converting them into nitrates. The improper use of medications in your aquarium may also destroy your nitrifying bacteria.

Chemically speaking, ammonia consists of a nitrogen atom and three hydrogen atoms. Each hydrogen atom is bound (chemically bonded) to the nitrogen. Ammonia can be represented by its chemical formula, NH3. In water, ammonia self ionizes into an ammonium ion (NH4+) and a hydroxide ion (OH-). The following chemical equations represent this interaction:



NH3 + H2O NH4+ + OH-


All the species in the equation are said to be in equilibrium (which is represented by the double arrow). That means that all species are present at all times, the concentrations of which are dependent upon varying factors, some of which will be discussed later.

Ammonium ions are virtually non-toxic to aquatic life in the concentrations that can occur in an aquarium.

Ammonia, on the other hand, is highly toxic to fish. It damages fish gills, effectively burning the soft tissue, making it difficult and ultimately impossible for respiration (oxygen exchange) to occur. It can be lethal in concentrations of 0.2 mg/L or lower depending on the species present and the amount of time they are exposed to the ammonia. Signs of ammonia poisoning are red or bleeding gills and the fish may appear to be gasping for air at the surface of the water.

Ammonia is colorless and odorless (in concentrations related to aquariums). Chemically speaking, ammonia is considered a weak base. The only way to know if it is present is by testing your aquarium water. Most aquarium grade ammonia test kits test the “total ammonia nitrogen” (TAN, also referred to as N-NH3) concentration that is present in a sample of water. The total ammonia is the amount of ammonia (sometimes referred to as unionized ammonia) and ammonium (sometimes referred to as ionized ammonia) present:



Total ammonia nitrogen = ammonia + ammonium
or
N-NH3 = NH3 + NH4+
Total ammonia levels should always test out as zero. If the total ammonia is not zero, be aware that only a fraction of the total ammonia reading is the toxic ammonia and the other fraction is the non-toxic ammonium ions. We will discuss how pH and temperature effect what fraction of the total ammonia is the toxic ammonia, but recognize that any ammonia present is a danger to your aquatic livestock.

When any total ammonia is detected, the fraction that is ammonia (NH3) increases with increasing temperatures. This effect is nominal, but nonetheless should be noted.

Understanding how pH affects the percent of ammonia present in a total ammonia concentration requires a quick review of water and how pH is defined. It is important to understand that water self ionizes. Two water molecules will interact with each other; a hydrogen atom will leave one water molecule for another water molecule, resulting in the formation of a hydronium ion (H3O+) and hydroxide ion (OH-):

H2O + H2O H3O+ + OH-


This only happens to a small percentage of the water molecules in a given solution. In looking at the above equilibrium expression for the ionization of water, we say the equilibrium is shifted to the left. That is that most of the water is not ionized and only a small portion of it is ionized.

The pH of a solution is a measurement of the hydronium ion (H3O+) concentration and ranges on a scale from 1 to 14. When the concentration of the hydronium ion is equal to that of the hydroxide ion, the pH is 7 and the solution is neutral (neither acidic nor basic). When the concentration of the hydronium ion is greater than the concentration of the hydroxide ion, the pH is less than 7 and is considered acidic. Conversely, when the concentration of the hydroxide ion is greater than the concentration of the hydronium ion, the pH is greater than 7 and is considered basic. We can summarize this in the following way (the brackets represent “the concentration of” the species inside them):

[H3O+] = [OH-]; pH = 7 (neutral)
[H3O+] > [OH-]; pH < 7 (acidic)
[OH-] > [H3O+]; pH > 7 (basic)

One thing that is important to understand is that even though a solution is acidic, there are still hydroxide ions present; they are just in a lower concentration than the hydronium ions. The opposite is also true.

The pH of an aquarium has a greater effect than temperature on the percent of ammonia (NH3) present when any total ammonia (TAN) is detected. The higher the pH, the higher the percentage of the total ammonia is present as NH3. A one unit difference of pH corresponds to a 10-fold increase in the percentage of NH3 present. We can see the effect of pH if we revisit the ionization of ammonia in water:

NH3 + H2O NH4+ + OH-


The pH of a solution is related to the hydroxide ion (OH-) concentration. Without detailing the mathematics, the higher the hydroxide ion concentration, the higher the pH (becomes more basic).

By definition, a pH greater than 7 corresponds to a greater number of hydroxide ions present than hydronium ions. What this does is shift the equilibrium expression for ammonia to the left. In other words, if more hydroxide ions are present, it will force ammonium ions to convert to ammonia. The higher the pH, the greater the equilibrium shift to the left will be and the higher the amount of total ammonia will be ammonia (NH3).

As the concentration of hydroxide ions lowers, the pH of a solution lowers. In regards to the equilibrium of ammonia, as the hydroxide ion concentration lowers, the equilibrium will shift to the right and ammonia will be converted into the less toxic ammonium ions. The bottom line is that at a higher pH, the amount of total ammonia that is present as toxic ammonia (NH3) is greater than it would be at a lower pH.

If you find that ammonia is present in your tank there are some steps you can take to reduce the ammonia concentration and the possibility that ammonia will cause damage to your fish. If you are cycling your tank with fish (NOT recommended, please see the article on fishless cycling), you will find high amounts (amounts greater than 0.20 mg/L) of total ammonia daily and will need to carry out large water changes. Even if your tank has cycled properly, but you are finding ammonia present, there are a number of procedures you can carry out to help ease the issue.


Large water changes will help dilute the ammonia concentration.
Since fish produce ammonia as part of their metabolic processes, the reduction or elimination of feeding your fish until the ammonia is undetectable in your aquarium will help reduce the amount of ammonia produced by your livestock.
Reduce the amount of livestock in your aquarium temporarily.
There are water conditioners on the market that can eliminate ammonia from your tank.

One such water conditioner, AmQuel (a Kordon product), safely and effectively removes ammonia (NH3) in a straight-forward method. The active ingredient in AmQuel is sodium hydroxymethanesulfonate, represented as NaCH2(OH)SO3. In solution, this chemical dissolves into two ions:

NaCH2(OH)SO3 Na+ + CH2(OH)SO3-


The hydroxymethanesulfonate ion [CH2(OH)SO3-], has the carbon atom as the central atom, for the purposes of our discussion. It has a hydroxy group (-OH) bound through the oxygen atom to the carbon atom, a sulfite group (-SO3) bound through the sulfur atom to the carbon atom and two hydrogen atoms (-H) each bound to the carbon atom (see below for a pictorial representation). When the hydroxymethanesulfonate ion comes into contact with an ammonia molecule, one of the hydrogen atoms from the ammonia molecule reacts with the hydroxy group to form a molecule of water. The remainder of the ammonia molecule binds to the carbon of the methanesulfonate ion through the nitrogen of the ammonia, resulting in a species called an aminomethanesulfonate ion. This reaction can be represented by the following equations (please note some species are rearranged for simplicity):


hydroxymethanesulfonate ion + ammonia aminomethanesulfonate ion + water

(HO)CH2SO3- + NH3 (H2N)CH2SO3- + H2O




The amino group (-NH2), formerly ammonia, stays bound to the carbon and does not release back into the water. It should be noted that the nitrogen of the amino group in the aminomethanesulfonate ion is still available to the nitrifying bacteria in your tank and will eventually be converted into a nitrate ion (NO3-). The nitrate ion is only removed by water changes or via plant uptake, as nitrate is a plant nutrient. It should also be noted that ammonia (NH3) is also a plant nutrient, but if it is present in detectable amounts in your aquarium, plant uptake will not occur fast enough to lower your ammonia readings to acceptable (no detection) levels.

Any unreacted AmQuel will remain in your tank unless removed by water changes or via activated carbon. It will continue to react with ammonia until it is exhausted. Information regarding other products that claim to remove ammonia was not readily available at the time of writing, but it is suspected they work in a similar fashion.

It is important to be aware that not all water conditioners are the same. You need to read each bottle carefully as they may have different uses. For example, the active chemical in dechlorinators is a substance called sodium thiosulfate. As more water companies are turning to chloramines to disinfect the public water supply, it is important to realize that sodium thiosulfate will neutralize the chlorine from chloramines, but creates ammonia that is released into you aquarium water as a by-product. Sodium thiosulfate does not react with ammonia. So using a dechlorinator in chloramine treated water will produce ammonia in your tank that needs to be dealt with. For more information about water disinfectants, please read the article regarding chlorine and chloramines.

Having ammonia present in an aquarium can be lethal to aquatic livestock. If detected early enough, there are actions you can take to minimize any damage done to your tank inhabitants. If your tank water tests positive for total ammonia (ammonia and ammonium), there are different factors such as the temperature and pH of your tank that effect the fraction of toxic ammonia (NH3) present of that total ammonia reading. Regardless, any ammonia is dangerous and hopefully after reading this article, you will have a better understanding of the role ammonia plays in you aquarium and how to deal with ammonia if it is detectable in your tank.



For more articles relate to fresh water aquariums care, please visit http://www.tropicalresources.net/phpBB2/articles.php

Great addition to the Articles section Ruby!!!!! Thank you

it worths for a pin topic, isnt it, anyway it is my pleaseure to post a helpful article

you should put some more cut and paste articles up like you did over at USA FHruby!!! There are a few more good ones that members here could use also. Especially that medications table one, PH one and Ich one, good information!!

Pinned! Post some more up if you gott em!

Spraying windex to clean an set-up aquarium isn't smart either. Ammonia! I've read stories of fish losing scales a few hours after cleaning their tanks with windex

if you spray windex on a paper tower from a distance then using it to wipe the outside glass of the tank it should be ok.
I done this all the time with my fresh and salt water tanks. Just make sure you wash your hands afterward with hot water before you stick your hand in the tank again.

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Rudy if you would like to post this article here please get permission from Tropical Resources or we do not have the legal right to keep this article on the site.

yeah, if you post those ones from fhusa that might be a good idea to check also ruby. Would hate to see you get in trouble my friend. Great information though, so hopefully you can get the permission. Sure they wouldn't mind a link to there website if they won't let you post article here.