The most important criteria to consider with a lake or fishery is the amount of dissolved oxygen (DO) in the water. Just like us, fish need oxygen to survive, so how do you know if you have enough oxygen in the lake? Oxygen is typically measured in Parts per Million (PPM) and you should be aiming for a minimum DO level of between 4 and 5 PPM.
If the amount of dissolved oxygen is lower than 4 to 5 ppm you put the fish in the lake at risk of dying through suffocation. It's particularly important when managing a fishery to pay attention to oxygen levels in the water because of the high number of fish using oxygen.
Stratification, or an oxygen deficient layer of water at the foot of the pond is another possible side effect of low oxygen levels, this can cause plant life in that layer of the water to die off. It it's not removed it will rot causing silt to build up increasing the build up of nitrate, nitrites and ammonias. Eventually this leads to a build up in ammonia. In addition you risk releasing dangerous toxins in to the atmosphere from potential anaerobic waste digestion.
What causes low dissolved oxygen levels in a lake or fishery?
Excessive amounts of algae and aquatic plants, will absorb a lot of oxygen after nightfall. An abundance of organic waste i.e high silt levels will alos cause oxygen levels to be reduced and silt can also release harmful gasses into the water. Also having a highly stocked fishery will reduce the oxygen levels.
In a natural, balanced and well managed lake, there would be little need for aeration but due to pressures exerted on many fisheries, especially during the spring and summer season, supplementary aeration is an essential management tool.
Oxygenation is not just important for fish, as virtually all biological processes that take place within water are dependent on a readily-available supplies of oxygen. The dependency on oxygen is crucial at every level, including the microscopic bacteria that are needed to process organic waste, the oxidisation of silt, the processing of nutrients or harmful gasses and the countless other systems that are required to maintain a healthy lake.
The best way to counteract a low oxygen level in the water is to install an aeration system. For more shallow fisheries, a surface aerator might be the best investment. Water is pulled from the top layer of the lake's surface and dispersed on top of the surface. Upon landing it facilitates an oxygen exchange helping to aerate the top few feet of the lake's surface. If however you have a deeper lake, a bottom based diffuser system that pulls air from above the surface in high volumes and smashes it into the water at the base of the lake enabling higher oxygen transfer, would probably be the best solution. A bottom based diffuser system would also help to reduce the threat of stratification as sufficient oxygen levels at the foot of the lake are maintained at a high level.
Aerators are very beneficial, not only do they protect your fish by maintaining healthy oxygen levels, they constantly stimulate good aerobic bacteria and eliminate unwanted nutrients, which are a cause of Algae outbreaks or blooms. Noxious smells are also reduced and overall water quality is improved. Silt reduction is also a benefit of increased oxygen.
While aeration systems are certainly not cheap they are an important investment for a lake that will save you time and money in the long run. Heathland Aquatic Engineering has a vast range of aerators, which with the help of our experienced team of engineers, enables us to choose the aerator that best suits your needs.
We can supply all the Fishery and aeration equipment you need and our services are available to domestic and commercial clients throughout Norfolk, Suffolk, Essex, London, Kent and United Kingdom. For more information and advice about any of our products such as pond and lake construction, pond and lake maintenance and cleaning and our expert fishery and consultancy services, please email [email protected] or call 0800 3891990.