Ammonia's Impact on Marine Life and Your Aquarium

Warning, Warning, Warning...Trace levels of ammonia can prove fatal to both saltwater and tropical livestock. Too bad this type of warning can't be displayed in a highly visible place, like smoking and cancer, alcohol and birth defects or operating heavy machinery and driving impairment issues, to aquarists. Ammonia in its most toxic form(NH3) can kill fish, invertebrates and corals alike as it is not selective. What you may not know regarding ammonia in the initial step of the nitrogen cycle has been linked to mortality and eventually tank wipe out if not contained and removed effectively and efficiently.

Ammonia represents the initial stage of the Nitrogen Cycle. It comes in two forms: free form (un-ionized) which is more commonly expressed as NH3 and a less toxic form called ammonium (ionized) and is represented as NH4. Water contains protons. The pKa or equal concentration level of both ammonium and ammonia is maintained at a pH level of roughly 9.3. The lower the pH level of water the higher the number of protons the water will have. Ammonia/ammonium levels work in opposite directions given varying pH levels. The higher the pH level is the greater the ammonia level will be and the lower the proton count water will have. Conversely, the lower the pH level of water, the greater the ammonium level will be as well as the amount of protons.

Dead or decaying food and animals can have an impact on ammonia levels. Ammonia is also excreted by fish and other heterotrophs through their gills and urine to a lesser degree. Basically, any living animal that feeds on organic matter and is not photosynthesis is responsible for creating ammonia. Quarantine and hospital tanks, low dissolved oxygen levels, synthetic salt mixes and bag water can also contribute to ammonia levels in aquarium water. An ammonia level greater than .0001 is toxic to most living life forms. Care must be taken to ensure that these levels do not exceed this magic number, or you are asking for trouble in the form of dead animals.

Ammonia is converted or oxidized to form nitrites(NO2) which in turn is further oxidized to form Nitrates(NO3) through one or more forms of bacteria. The three forms of bacteria are Nitrosomanas, Nitrosospiras and Nitrosococcus with varying strains and species contributing to this oxidation process. Ammonia is also consumed by organisms to form proteins and other biomolecules needed to build tissue. Algae, both micro and macro forms, consumes nitrates for survival though a biochemical pathway where the algae has to reduce nitrates to ammonia before it can use it, hence the reduction of ammonia.

Toxicity of ammonia in heterotrophs, such as fish, can be expressed as such. Fish passively diffuse ammonia through their cells such as gills as a pathway of excretion, hence the need for a lesser gradient in order for the fish to be able to perform this. If ammonia is allowed to increase above this .0001 mark what is essentially happening is this gradient is reversing itself. In doing so, the fish is finding it increasingly more difficult to rid its body of ammonia in the body. Eventually, this process can stop leading to limited or no oxygen in the blood, causing suffocation and ultimately death of the fish. This same philosophy holds true with salinity levels and freshwater stored in a fishes body.

Water changes, the nitrogen cycle and ammonia. Many aquarists swear by the urban legend that performing a water change will reduce the amount of ammonia present in aquarium water. Usually aquarists rely on this method in efforts of not only speeding up the initial cycle of their new tank but in hopes of reducing ammonia, nitrites and nitrates. Often times this only prolongs the whole scenario aside from the ability to reduce nitrate levels through water changes. One of the worst things to do during a cycle is a water change. Basically, what happens is, initially your ammonia, nitrite and nitrate levels may subside, but only temporarily. The reason being is that your pH level in your tank may spiral downward somewhat due to the addition and replenishment of pure, new saltwater. This causes the elevation of the less toxic form of ammonia in the form of ammonium. We know this now because, remember ammonia and ammonium increase and lower based on pH levels above the pKa equality line of 9.3. The buffers in synthetic salts will tend to reduce pH somewhat during a water change. This, however, is only short lived as the pH levels will eventually shift upward causing ammonium(NH4) to switch to the toxic form ammonia(NH3). Moreover, many synthetic salt mixes contain ammonia due to the process in which they are made, such as the Solvay process which apparently uses ammonia in the manufacturing process. The best thing to do during a cycle is nothing! Let nature takes its course and allow the bacteria to grow to breakdown the ammonia, nitrites and nitrates associated with the nitrogen cycle. Be patient and go slow. The end result will please you and also be safer for your livestock.

Hopefully, this article will clarify some of the misconceptions and demonstrate the severity that ammonia poses in the marine aquarium. Establishing ways of reducing and hopefully eliminating ammonia from your aquarium is your best defense in creating and maintaining a healthy and beautiful marine aquarium. This combined with compatibility and husbandry requirements being met, varied diet, stable water parameters, proper filtration and maintenance and not exceeding the bioload recommendations for your particular sized aquarium will ensure long term success.