Ammonium / ammonia
Overview
Ammonium in Koi ponds primarily arises through degradation of proteins. It is secreted by the Koi as an end product through its gills and urine. Ammonium is less toxic. The accompanying ammonia, however, is toxic in lowest concentrations. This is reduced by nitrification (see nitrate) under consumption of oxygen in a biological process to nitrate. In ponds that are overpopulated, or have not adequate filter bacteria, toxic ammonia can accumulate. Ammonium / ammonia in the water from 0.5 to 1 mg / l, depending on the pH of the water, are classified as critical for fish.
Further information
Common
The ammonium ion NH4 + is a cat ion which arises through protein decomposition in nature. It is one side secreted by aquatic organisms, and on the other side produced in the decay of biomass. In a Koi pond usually the Koi is the main producer, which secrets ammonium through the gills (75%) and urine (about 25%). Ammonium is the conjugated acid of the strong toxic base ammonia (NH3). Ammonium forms a dissociation balance with it. This balance dependent on the pH value of the water- and is therefore not constant. The proportion of ammonia increases with increasing pH and increasing temperature. Ammonia becomes, by nitrification of bacteria in two steps, first to nitrite, than to relatively non-toxic nitrate. For this bacteria need large amounts of oxygen. This is withdrawn from the water. It must be ensured that the pond water is adequately ventilated.
Toxicity
Ammonium is less toxic, but ammonia is very toxic for living organisms. Ammonia reacts in the body similar to the potassium ion and may instead be used by the body. Here it reacts as a powerful nerve poison.
Limit
It must be ensured that the value of ammonia in the pond is always at 0 mg / l. If the value rises, rapid measures have to be taken. A water exchange up to 100% is an effective emergency measure, but usually without long-term effect. A partial water exchange should already be made, at more than 0.2 mg / l, since this value often reported as toxic. Long time measures, such as additional ventilation or bacteria injections (both increases nitrification) must be made accompanying.
Factors which influence the ammonium / ammonia content
Oxygen concentration
pH Value
Retention time in the filter
Pollution by bio-mass
Fish stocking
