Avoid Fish Fatalities In Garden Ponds Control Ammonia Levels

What is ammonia And How Can It Be Controlled?

Ammonia is a chemical compound that in high concentrations is potentially lethal to all pond fish. No doubt you will have come across other water gardening and pond keeping articles on the internet relating to biological pond filters and their function in breaking down ammonia. Ammonia is much talked about by pond keepers and once you understand a bit more about this chemical you will understand why ...

The aim of this pond keeping article is to try to help you to understand how ammonia appears in your garden pond and what you can do to keep ammonia concentrations in your garden pond at a safe level. There is only one way to handle consistently high concentrations in your garden pond until the cause has been identified and that is to carry out routine pond water changes. A major way to reduce ammonia concentrations in any aquatic garden pond is to stop feeding your pond fish, particularly large Koi as they eat plenty and produce high levels of ammonia through their feces and urine.

Where Does Ammonia In my Pond Come From?

The vast majority of ammonia in your pond is excreted into the pond as the metabolic waste produced by Koi, goldfish and other pond fish as they eat. Like all humans pond fish need to eat in order to grow and develop. Unlike humans however they live in their own toilet and are unable to escape their surroundings; your garden pond.

In chemical terms ammonia (NH3) is produced from the proteins that we eat. Proteins are made up of chains of amino acids, which contain the chemical element Nitrogen. Unfortunately for us pond keepers who feed our pond fish to watch them grow bigger, stronger and more colorful are in effect encouraging them to poison themselves; that is unless we control the levels of ammonia within our garden pond.

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 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 practically zero. If only this was the case in garden ponds.

How Does Ammonia Present Itself In Garden Ponds?

Over feeding of pond fish and inadequate biological filtration in fish ponds can be catastrophic to the Koi and goldfish population. 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 will change this equilibrium.

Take a look below to see the affects different pond pH levels have on the amount of potentially lethal ammonia ...

At pH7 or less ammonia isn’t present; only ammonium is present. This is ideal as ammonium is far less harmful to pond fish.
At pH8 there is 95% ammonium and 5% ammonia.
At pH 9 all things are equal as the concentration of ammonia id 50% and the concentration of ammonium is 50%. This is a bad state of affairs and things are starting to look terminal.
At pH11 only ammonia is present. It is too late at this stage as your Koi, gold fish and other pond fish are more than likely dead.

Ammonia concentrations even if stable pH conditions exist in your garden pond can still cause problems, particularly when the pond water temperatures are high.

The table below shows the long term level in parts per million (ppm) of ammonia or ammonium depending upon the pH and pond water temperature. You will see that as the pH level raises your pond fish tolerance to ammonia levels is significantly less. As the temperature rises the tolerance level is even less.

	Water Temperature In Celsius
pH	20 C	25 C
6.5	15.4	11.1
7.0	5.0	3.6
7.5	1.6	1.2
8.0	0.5	0.4

Many garden ponds have pH levels of 9, particularly when there is a large amount of green pond causing algae. Your garden pond is lacking in alkalinity. This is another extremely important reason why I would recommend using a UV sterilizer (UV clarifier) in your garden pond, even if you use an excellent biological pond filter to control ammonia build up. Excessive amounts of floating pond algae are not good as they can cause rapid fluctuations in pond pH levels.

How Do I Control Ammonia Levels in My Garden Pond?

According to some statistics that I came across on the internet between 3% and 4% of the Koi food fed to Koi is excreted into the pond water as ammonia. The article was written by Gerry Preston, who writes Koi keeping articles for the UK magazine Nishikigoi International. Gerry also states that it is far better to feed Koi on a more regular smaller portion basis.

The best solution for controlling ammonia levels in garden ponds is to use a correctly specified biological pond filter, which takes into account the size of your pond, the fish stocking density and also any future increases in fish loads. The pond filter will also need to be able to handle the increase in fish size as they grow and develop.

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. A biological pond filter mimics this naturally occurring process, making your garden pond a safe and healthy environment for Koi, goldfish and other pond fish species to live in. For the nitrogen cycle to be carried out efficiently large amounts of oxygen are required. Garden ponds can never have too much oxygen. That is why it is advisable to maximize pond oxygen levels by incorporating a cascading waterfall or pond air pump into your garden pond.

Just to show the levels of oxygen needed for Nitrosomonas and Nitrobacter nitrifying bacteria to convert ammonia into nitrites and then into nitrates, take a look at the 2 equations below ...

For Nitrosomonas: 55NH4+ + 76O2 + 109HCO3- ---> C5H7O2N + 54NO2- + 57H2O + 104H2CO3
For Nitrobacter: 400NO2- + NH4+ + 4H2CO3 + HCO3- + 195O2 ---> C5H7O2N + 3H2O + 400NO3-

Don’t worry if you don’t understand the equation, the main thing to notice is that the levels of oxygen (O2) needed. Have you ever noticed that during hot weather your pond fish appear to be gasping at the pond surface for oxygen? The reason for this is because as pond water temperatures rise it becomes increasingly more difficult for oxygen to dissolve in the pond water. 4.3 mg of oxygen is required by Nitrosomonas and Nitrobacter beneficial bacteria when converting 1 mg of ammonia into nitrates.