Water Quality Monitoring - assessment & advice. 

We recognise that fish health issues are often related to other factors, such as water quality & habitat issues, so we also offer a full water quality analysis & habitat assessment service.

 Analysis carried out by Blueroof (under laboratory conditions):

(NB: un-ionised ammonia levels are calculated using a reference graph & sample temperature and pH results.)

Field meter readings were taken by Blueroof:                                                   

Phosphates – This chemical is not thought to be directly toxic to fish. Phosphates are a plant nutrient and high levels (re potential ‘eutrophication’) are considered to be anything more than 0.1 mg/l).

Ideally levels should be less than 0.03mg/l. Between 0.03mg/l and 0.06mg/l there could be an increased risk of fish deaths in winter, although coarse fish will probably be ok, levels above 0.6mg/l indicate a serious risk of fish kills over winter.

Nitrate – This chemical is not thought to be directly toxic to fish and is another plant nutrient. It may act as a limiting factor on the growth of plants and algae if levels are low. High levels, generally concentrations above 30 mg/l, are indicative of existing or potential problems of ‘eutrophication’. This is the enrichment of water by nutrients, especially compounds of nitrogen and/or phosphorus, causing accelerated growth of algae and higher plant forms to produce an imbalance of organisms present in the water and a reduction in the quality of the water.

Nitrite - This compound is directly toxic to fish at levels of 10-20mg/l. Nitrite is formed as ammonia is changed, by naturally occurring bacteria, in the presence of oxygen, into nitrite (NO₂^-). Another species of bacteria changes nitrite to nitrate. 

Ammonia – This is a breakdown, product created during the metabolism of most animals. It exists in two forms in water, ionised (NH₄⁺) and un-ionised (NH₃). The un-ionised form of ammonia is toxic and can, above certain levels, put fish under stress (leaving them less able to cope with reduced dissolved oxygen levels for example) and at higher levels it is directly toxic to fish. The proportion of total ammonia that is un-ionised, and is therefore potentially harmful, increases with both temperature & pH.

Ideally, levels of un-ionised ammonia should be at less than 0.03mg/l and certainly we are concerned about levels at or above 0.1mg/l. It is shown to be directly toxic to fish at levels of 0.3mg/l.

Dissolved Oxygen concentration (DO) – this will measure the oxygen level of the water, which is influenced by several factors:

·        surface disturbance entraining oxygen into the water.

·        aquatic plants photosynthesising during daylight hours.

·        respiration of aquatic organisms, including plants/algae during the night.

The oxygen content of a the water body varies during the day, being at its lowest at dawn.

The level should not be allowed to fall below 8mg/l.

pH – This is a measure of the acidity or alkalinity of the water. It is influenced primarily by the amount of carbon dioxide produced by aquatic animals.

We would expect to see pH in the range 6.0 to 9.0.

Conductivity – This records the ability of the water to conduct an electric current. It is linked to the level of total dissolved solids in the water. As such, changes in conductivity will give us a quick indication of changes in nutrient levels in the water (phosphates, nitrates, etc).

Biochemical Oxygen Demand (BOD) – This measures the amount of oxygen removed from the water in 5 days. Lake water contains vast numbers of bacteria and fungi, most of which live by breaking down organic material, using oxygen in the process. BOD is a measure of how quickly these organisms use oxygen and so gives an indication of the numbers of these organisms and thereby the levels of organic material in the water body. High levels (much above 2.5mg/l) may indicate a risk of low oxygen levels at certain times. Levels above 5mg/l are of concern.

Fish health status – Growth rates, age, size range, presence of disease causing organisms and signs of nutritional imbalance all give indications of the overall health status of the fish population.

Ecological surveys.

Benthic Invertebrate sampling & identification.

Pollution investigations