Ammonia is a toxic compound that is extremely lethal to pond fish, particularly in high concentrations. This short article will hopefully give you an insight into how ammonia appears in your garden pond and how fluctuations in pond water temperature and algae levels influence the concentrations.
How Does Ammonia Get Into Garden Ponds?
Ammonia can appear in your pond from a variety of sources, including rotting organic matter on the pond floor, dead and decaying aquatic life and uneaten fish food. However the vast majority of ammonia found in a pond environment is the direct result of pond fish feeding! Koi, goldfish and other pond fish need to eat to grow. As they eat they produce bodily waste, which contains high levels of ammonia.
How Is Ammonia Produced?
Ammonia is produced from the proteins that pond fish eat. Proteins are made up of chains of amino acids, which contain the chemical element Nitrogen. Unlike natural lakes and ponds which contain large volumes of water a garden pond, even a large Koi pond is small in comparison. In terms of water volume and fish stocking levels, garden ponds are far more crowded. In nature, ammonia levels hardly ever reach toxic levels because as a percentage of the water volume it is insignificant.
How Does Ammonia Present Itself In Garden Ponds?
Over feeding of pond fish and inadequate biological filtration is a sure sign that your pond will suffer from higher than needed ammonia levels. Ammonia is present in garden ponds as ammonia (lethal) or ammonium (less toxic). Ammonium constantly converts itself into ammonia and hydrogen ions and vice versa. A balanced equilibrium is found. However a change in pond water pH or pond water temperature affects this delicate equilibrium. At a pH of 7 there is only ammonium present. Compare this with a pH of 9 where there is 50% ammonia and 50% ammonium. The alarm bells should start to ring. At a pH of 11 there is only ammonia present. At this late stage all your pond fish will have been poisoned and will have died.
How Do I Control Ammonia Levels in My Garden Pond?
The best solution for controlling ammonia levels in garden ponds is to use a correctly specified biological pond filter, also known as a pond filter or biofilter. A correctly specified bio filtration system will safely control the build up of ammonia. Always choose a pond filter that is bigger than you need as this will allow for increases in the number of fish you keep, along with an increase in fish size; bigger fish eat more and produce more waste, resulting in more ammonia.
What Is The Nitrogen Cycle?
The process of converting ammonia compounds into nitrates is carried out by Nitrosomonas and Nitrobacter beneficial bacteria in a chemical process known as the Nitrogen Cycle or Nitrification process. In a garden pond these beneficial bacteria colonize the pond filter media housed in your pond filter. The chemical process of actively converting ammonia into nitrates in the nitrogen cycle requires vast quantities of oxygen. That is why it is advisable to maximize pond oxygen levels by incorporating a cascading waterfall or pond air pump into your system.
Take a look at the equations below which shows just how much oxygen is required.
By Nitrosomonas:
55NH4+ + 76O2 + 109HCO3- --> C5H7O2N + 54NO2- + 57H2O + 104H2CO3
By Nitrobacter:
400NO2- + NH4+ + 4H2CO3 + HCO3- + 195O2 --> C5H7O2N + 3H2O + 400NO3-
As you can see oxygen (O2) is needed extensively for these processes to take place. As pond water temperatures rise in summer it becomes increasingly more difficult for oxygen to dissolve into water, further increasing the opportunity for ammonia levels to increase. 4.3 mg of oxygen is required by Nitrosomonas and Nitrobacter beneficial bacteria when converting 1 mg of ammonia into nitrates.
