Water quality assessment
Water quality testing In order to fully evaluate the relationship between the fish and its water environment, sampling should be performed at routine intervals throughout the day to create a complete profile of the water quality.
Water quality testing check-list:
Water quality testing check-list:
- Sampling at routine intervals
- Test selectively – not following feeding periods
- Regular or continuous testing of quality parameters:
- Dissolved oxygen
- Temperature
- pH
- Ammonia
- Nitrite and nitrate
Dissolved oxygen
The respiration and ventilation rate of fish is dependent on the dissolved oxygen (DO) content in water. Different fish species, sizes and temperature of the water will determine their metabolic rates, and hence the amount of oxygen they require. DO levels can be easily measured by DO meters (mg L-1 or % saturation), which require the submersion of a probe in the water sample.
It is important to note that:
The respiration and ventilation rate of fish is dependent on the dissolved oxygen (DO) content in water. Different fish species, sizes and temperature of the water will determine their metabolic rates, and hence the amount of oxygen they require. DO levels can be easily measured by DO meters (mg L-1 or % saturation), which require the submersion of a probe in the water sample.
It is important to note that:
- The smaller the fish, the higher the metabolism, the more oxygen it will consume
- Warm water fish require lower DO levels than cold water fish
- At higher water temperatures and increasing altitudes and salinities, the amount of oxygen that can be dissolved in water decreases.
Temperature
Each species of fish have different water temperature tolerance and they can be distinguished into temperature regimes such as cold water, warm water, cool water and tropical. As fish are ectoderms, it is important to maintain the appropriate water temperature for them to regulate their bodies. Temperature can be measured with a thermometer, reversible numeric liquid crystal strips, thermocouples or a temperature probe combined with a DO meter.
pH, Ammonia, Nitrite and Nitrate
Test kits such as the API Freshwater Master Test Kit are readily available to measure pH, ammonia, nitrite and nitrate levels in water.
Each species of fish have different water temperature tolerance and they can be distinguished into temperature regimes such as cold water, warm water, cool water and tropical. As fish are ectoderms, it is important to maintain the appropriate water temperature for them to regulate their bodies. Temperature can be measured with a thermometer, reversible numeric liquid crystal strips, thermocouples or a temperature probe combined with a DO meter.
pH, Ammonia, Nitrite and Nitrate
Test kits such as the API Freshwater Master Test Kit are readily available to measure pH, ammonia, nitrite and nitrate levels in water.
pH
The pH levels of water should be regularly tested to ensure the water is neural or slightly alkaline for marine fish.
To test pH:
Ammonia
The urine and solid waste of fish, uneaten food and decaying organic matter in water are all sources of ammonia, which are regulated by nitrifying bacteria. Ammonia levels are tested to check for imbalances in the water system.
To test ammonia (mg/L):
Nitrite
Nitrifying bacteria converts ammonia to nitrite, then to nitrate. Nitrite is toxic and small amounts are able to stress fish and suppress their immune system.
To test nitrite:
Nitrate
Nitrate levels indicate the amount of fish and organic wastes, where an excessive build-up can lead to algal blooms.
To measure nitrate levels:
The pH levels of water should be regularly tested to ensure the water is neural or slightly alkaline for marine fish.
To test pH:
- Fill a clean test tube with 5mL of the sample water.
- Add three drops of pH test solution and ensure the drops are uniform by holding the bottle vertically.
- Put the lid on the test tube and invert it several times.
- Match the colour of the solution against the pH colour chart to determine the pH level.Optimum pH ranges:
- Freshwater: 6.5 to 7.5
- Marine and estuarine water: 8.0 to 8.5
Ammonia
The urine and solid waste of fish, uneaten food and decaying organic matter in water are all sources of ammonia, which are regulated by nitrifying bacteria. Ammonia levels are tested to check for imbalances in the water system.
To test ammonia (mg/L):
- Fill a clean test tube with 5mL of the sample water.
- Add eight drops of ammonia test solution from Bottle 1 and ensure the drops are uniform by holding the bottle vertically.
- Add eight drops of ammonia test solution from Bottle 2, also ensuring the uniformity of the drops.
- Put the lid on the test tube and shake it for 5 seconds, and wait 5 minutes for the solution to develop.
- Match the colour of the solution against the ammonia colour chart to determine the ammonia level, which should be 0mg/L in an established environment.
Nitrite
Nitrifying bacteria converts ammonia to nitrite, then to nitrate. Nitrite is toxic and small amounts are able to stress fish and suppress their immune system.
To test nitrite:
- Fill a clean test tube with 5mL of the sample water.
- Add five drops of the nitrite test solution and ensure the drops are uniform.
- Put the lid on the test tube and shake it for 5 seconds, and wait 5 minutes for the solution to develop.
- Match the colour of the solution against the nitrite colour chart to determine the nitrite level, which should be 0mg/L in an established environment.
Nitrate
Nitrate levels indicate the amount of fish and organic wastes, where an excessive build-up can lead to algal blooms.
To measure nitrate levels:
- Fill the clean test tube with 5mL of the sample water.
- Add ten drops of nitrate test solution from Bottle 1, ensuring the drops are uniform.
- Put the lid on the test tube and invert it several times.
- Shake Bottle 2 for at least 30 seconds.
- Add ten uniform drops from Bottle 2 into the same test tube.
- Put the lid on the test tube and shake for one minute, and wait for 5 minutes for the solution to develop.
- Match the colour of the solution against the nitrate colour chart to determine the nitrate level. The recommended nitrate level is 40mg/L.