Ammonium (NH4) and ammonia (NH3) are chemical compounds.
Ammonium (NH4) reacts to very toxic ammonia (NH3) in case of high pH values and elevated temperatures (typical for salt water aquariums). Ammonia is a chemical compound consisting of nitrogen and hydrogen and is created during the natural decomposition of dead plants and animals as well as animal excrements.
An overconcentration of ammonia can be reduced through an efficient nitrification (e.g. promoted by starter bacteria) and through a regular water exchange. Suddenly occurring elevated ammonia concentrations (e.g. resulting from dead animals) should immediately be removed by a generous water exchange.
Ammonia is very poisonous to all aquarium species and should therefore be measured regularly. The GIESEMANN NH3 test analyses the total ammonium, which is the sum of ammonium (NH4) and ammonia (NH3). This test is specifically developed for sea water aquariums, i.e. for salt water.
The total value of ammonium in the aquarium should be below 0.2 mg/l.