What is ammonia NH3 & NH4?

Ammonia is pased from the gills of fish in there urine, also rotting food and decaying plant matter are contributors of ammonia.

It exists in two forms in the aquarium and the first step is to understand the difference between ammonium NH4 and free ammonia NH3.
 

NH3 (ammonia) is a gas and sometimes called toxic or free ammonia. It is the unionised form of NH4.

NH4 (ammonium) is a nontoxic salt it is the ionised form of ammonia.

NH3 and NH4 together are often refered to as total ammonia nitrogen (TAN). 

So as you can see from above NH3 is the nasty toxic element that needs monitoring.

Most ammonia test kits measure TAN especially if they are marked as an NH3/NH4 test kit. The measurement is done by changing the pH of the water sample; you may have noticed how ammonia test kits normally have a small bottle marked harmfull corrosive.

Seneye only measures toxic free ammonia and in very low levels as its difficult to accuratly work out how much harmful NH3 is present by measuring NH4 and PH and then using a look up table.

Ammonia toxicity changes for different organisms but one thing is constant and that the desired level is as close to zero as is possible. Marine organisms and fish tend to be more sensitive and where as fish that have evolved to live in ponds or puddles such as carp or paridise fish tend to be less so.

As a rule of thumb and if measured directly we use the following chart.

NH3 is reported in the unit of ppm but this is interchangble with mg/L as it is a gas disolved in water.

 If your ammonia is very high you may find it useful to learn how to control ammonia.

Why does my free ammonia NH3 go up when I do water changes?

Can my seneye be used for cycling my aquarium?