norfolk fishing network - global fishing 2004 - 2023


Fish are highly dependent on the water in which they live. Therefore any changes in the water conditions will have a direct effect on the health and wellbeing of the fish.
There are several characteristics of water which must be kept within certain levels in order to provide conditions suitable for fish life.
The most important of these are the pH level (Acidity or alkalinity) and the level of toxic waste products (Ammonia, Nitrite, Nitrate).
It is important to test water for toxic waste and pH before any fish are introduced to a body of water, and take corrective action if necessary. It is also important to carry out regular checks of the water once it has been stocked with fish, so that any changes in the water conditions can be quickly identified and remidied before they lead to time consuming and expensive problems with fish health.

pH is the measure of the amount of a substance called hydrogen in the water. It is measured on the scale of 0-14. The mid point of the scale is 7, which is defined as neutral. Any pH below neutral(0 - 6.9) is called acid, and any pH above 7(7.1 - 14) is called Alkaline.

Fish require a pH of between 6.5 and 8.5. Outside of these levels fish are prone to stress, as well as gill, fin and tissue damage. his in turn makes the fish susceptible to disease. At extreme levels (above 10 and below 5) the water conditions will actually kill the fish.

The pH of a body of water consistently changing as a result of many factors (rain, photosynthesis by plants and algae, evaporation, and the production of fish waste etc.). It is therefore, extremely to regularly check the pH level of the water to ensure it remains within acceptable limits.
This should be done evey 2 weeks throughout the year, between April and September. During the Winter months, the factors that cause the pH to vary, are absent, therefore regular testing is not so vital.

Ammonia is very dangerous to fish. The exact level of toxicity depends on the water's pH and temperaute. Ammonia is at it's most dangerous when in high pH conditions(such as those found in smaller bodies of water) and high temperatures (i.e during the summer). At relatively low levels Ammonia will cause stress to fish, which may lead to fish disease and at higher levels can kill fish outright.

Nitrite is the result of the breakdown of Ammonia by naturally occuring bacteria. Fish ideally prefer water with little or no Nitrite (0 - 0.1 milligrams per litre). Outside these levels, ie. above 2 milligrams per litre, the water conditions become very dangerous for fish.

Nitrate build up in bodies of water is normally a slow process caused by successive breakdown of waste material. Nitrate is much less toxic than ammonia and nitrite. High levels of nitrate, however, do cause stress to fish which can make them more susceptible to fish disease. Nitrate is also extremely important because it is one of the major causes of green water and blanket weed algae problems

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