The water quality can not be judged solely by the clarity of the water. Test kits are available to measure a variety of chemical parameters which, if not within a specific range, may affect the quality of the pond water and the health of fish and pond wildlife.These kits are available as test strips, colour changing solutions or electrical meters.

In ponds the principal sources of ammonia are excretion by fish and the rotting of uneaten food, dead fish or plants. When ammonia is released into the water it may take one of two forms; Free Ammonia, which is highly toxic to fish, or Ammonium, which is not.Total Ammonia = Free Ammonia AmmoniumFree ammonia is formed at higher temperatures and pH levels, so the total ammonia in a more alkali pond in summer will be more toxic than the total ammonia in a more acidic pond during the winter. Most test kits will only measure the total ammonia present, so the temperature of the water and pH levels should be taken into account when considering the potential risk of the recorded ammonia levels.Ammonia is measured in milligrams per litre or parts per million, mg/l or ppm (both measurements translate to the same reading). Ideally the total ammonia in any pond should be zero, this would indicate that the pond’s biological filtration, which removes ammonia from the water, is coping as desired. It is recommended that the Free Ammonia levels should always be maintained below 0.02 mg/l.The table below shows the levels of total ammonia (mg/l) at which free ammonia will be at or below 0.02 mg/l, at a range of pH and temperatures.

Temp °C

pH

6.0

6.5

7.0

7.5

8.0

8.5

9.0

0

250

77

24

7.7

2.4

0.78

0.1

5

154

50

16

5

1.6

0.52

0.07

10

105

34

11

3.4

1.1

0.36

0.05

15

74

23

7.5

2.3

0.75

0.25

0.04

20

50

16

5

1.6

0.52

0.18

0.04

25

35

11

3.5

1.1

0.37

0.13

0.03

30

25

8

2.5

0.8

0.27

0.1

0.03

fish would display symptoms such as slime disease and will develop red and swollen gills. As ammonia levels rise further the fish are less able to absorb oxygen and will display signs as if there are low levels of oxygen in the water. At high levels the fish’s fins become red and ragged and their internal organs will become damaged.If ammonia levels rise in a pond then steps must be taken to counter the problem. Check the density of the fish stocks and make sure that fish are not being over fed. Remove any potential sources of ammonia such as uneaten food, dead fish or pond sludge. Improve the pond’s biological filtration, check it is well oxygenated and of an adequate size.In many cases an ammonia rise has occurred because too many fish have been added to the pond over a short period of time, or the biological filter has been poorly maintained and the filtration bacteria removed or killed. In this case it is recommended to add a filter start product to increase the bacterial population. If the ammonia level is at a worryingly high level then a partial water change should be carried out to dilute the ammonia levels before the source of the problem is treated, there are also ammonia removing treatments available for a short term remedy if the ammonia level is very high.