Many kinds of fish require clean, cool, well-oxygenated water. Water that is not properly aerated will have a low level of dissolved oxygen and will often have stratified water columns, or water that varies in water quality depending on the depth and level of the water.
Finding out the proper level of aeration often takes a trial-and-error approach. A commonly accepted method of finding the proper aeration is to pump the entire pond through the filter at least once per hour. This does not guarantee sufficient aeration, however, as the shape, size, and structure of your fish pond could necessitate a different level of aeration in order for the pond to be properly aerated.
An external filter could have the flow returned to the pond using a stream or waterfall. This can diffuse the current, which can lead to low-flow areas on the opposite side of the pond. Adding an additional outlet to the flow can usually correct this problem. Many people will add supplemental flow through an air pump or dedicated pump to ensure proper air flow throughout the entire pond.
Without proper aeration, there will be low dissolved oxygen levels in the water. If the dissolved oxygen levels are too low, it can cause many problems, with the most dangerous problem being that fish can die if a certain parts per million (ppm) of dissolved oxygen is not maintained.
Additionally, noxious odors can come from the pond when there are low levels of dissolved oxygen in the water. This is due to the breakdown of organic waste shifting from an aerobic process to a slower anaerobic process, which results in the formation of hydrogen sulfide (that produces the odor). If the pond is deeper, the lack of oxygen will also create an unusable layer at the bottom of the pond, a place where fish cannot inhabit. As a result, their living space is reduced and the oxygenated water in that living space is stressed even more because it alone has to sustain the fish.
The most common cause of low oxygen levels is an overabundance of aquatic plants, especially algae. A moderate number of aquatic plants can be beneficial to the pond because they do release water into the pond. Planktonic algae are the first step in the food chain of a pond, so their presence is also critical. However, having too many of them will harm the pond’s environment; while planktonic algae do provide oxygen to the pond during the day, they will also consume oxygen at night. As a result, heavy algae blooms or thick aquatic vegetation can lead to dangerous low levels of oxygen for the fish, often leading to their deaths.
Poor dissolved oxygen levels also come from high organic waste loads. Dead vegetation, fertilizer run-off, fish food, and fish waste can all contribute to the amount of organic waste load. These elements can be naturally broken down in a pond due to the presence of beneficial bacteria, but like most things, that bacteria needs oxygen in order to do it, which is why it is critical that you keep the oxygen levels at acceptable levels or higher.
To do this, you need to consider the two main types of aeration systems: surface aeration and bottom based aeration. To decide which would be more beneficial for your pond, consider the depth of your pond. If your pond is less than six feet deep, a surface aeration system is likely best, while deeper ponds should utilize a bottom based aeration system.
The main difference between the two types of aeration systems is that surface aerators are usually floating aeration units that pull in water from the top foot or two of the pond and splash it into the air. As the water falls back to the pond, oxygen transfer and the venting of gases occur. This means that the aeration is taking place just at the surface, which is why this method of aeration works best for smaller ponds.
Conversely, bottom based aeration systems or diffused aeration involves pushing air down to the bottom of the pond or lake and allowing the bubbles to rise naturally to the surface of the water. The bubbles provide the bulk of the aeration, which makes bottom based aeration systems the ideal choice for larger ponds and lakes. As the bubbles rise, they de-stratify the water, which eliminates that oxygen-poor zone down at the bottom of the pond or lake. The oxygen rich water helps to create a healthier water column.
Proper aeration will not only keep your fish alive, but will also stimulate beneficial pond bacteria that can break down waste and reduce the bottom muck layer. Aerobic bacteria will also be more numerous than anaerobic bacteria, which will reduce the odor that your pond produces. Phosphates, which algae thrive on, are eliminated, preventing the algae from accumulating in your pond. Your overall water quality will also be improved. Gasses like carbon dioxide and hydrogen sulfide can be easily vented. Quality aeration systems can also keep fish from dying in ponds in northern states during the winter, as the pond’s surface will not freeze over, allowing gasses to be vented during the winter, which is critical to the survival of your fish.
To further aid the presence and growth of aerobic bacteria, you should utilize EcoBio-Block nsM and/or EcoBio-Block Wave. These products have been shown to increase the presence of nitrifying bacteria and decrease the time it takes to establish the denitrification cycle in your pond. This will help to reduce the odor emanating from your pond and it has been established as safe for all fish and plants.
As you can see, pond aeration is critical to the survival of your fish and to the presence of aerobic bacteria, which can break down waste more quickly and with less odor than anaerobic bacteria. There are two main types of aeration: surface aeration and bottom based aeration. Surface aeration is best for ponds that are less than six feet, as aeration only occurs at the surface. For deeper ponds and lakes, bottom based aeration is best, since this keeps the bottom part of the pond/lake enriched with oxygen, critical to the water level remaining high and allowing your fish to live throughout the whole area. By carefully considering and implementing the proper aeration system, your fish can remain healthy and add to the landscape of your pond.