Where does the ammonia originate from?
Pond fish produce waste in the form of ammonia, which is released into the water through the gills. Ammonia can also originate from the dead and decaying plant material in the pond or from uneaten food, which is left in the water.
In an established pond with a functioning filtration system the ammonia is broken down by Nitrosomonas species of bacteria to a secondary product, known as nitrite.
Ammonia can exist in two forms when dissolved in water, the first is the free ammonia and this is very poisonous to fish, the second form is known as ionized ammonia which is not quite as harmful as the free form.
Ammonia can have a number of detrimental effects on pond fish such as disrupting the ability to regulate water and salts, it may also damage delicate gill tissue, causing swelling of the tissue which may hinder the absorbtion of oxygen from the water.
If the water becomes polluted with ammonia, regular partial water changes need to be undertaken to reduce the concentration of the pollutant.
In the early stages of establishing a filtration system on the pond, it may take several weeks before the ammonia level in the water begins to drop. | 
