Essential Pond Aeration Tips: Prevent Low Oxygen Levels

Essential Pond Aeration Tips: Prevent Low Oxygen Levels

Your backyard pond is a living ecosystem with a variety of aquatic life who require oxygen (O2) to survive and thrive. Fish, snails, and other organisms, must get oxygen from the pond water for their respiration. However, unlike land, oxygen is generally less available in aquatic environments. 

Pond aeration is the process of increasing or maintaining the amount of dissolved oxygen in a pond. In this blog post, we will explore the vital role of oxygen in the backyard pond and give aeration techniques to ensure a healthy and thriving ecosystem for your fish and plants. 

Oxygen Dynamics in Natural and Backyard Ponds 

In most natural ponds, oxygen is sourced in two ways: firstly, from the atmosphere through diffusion and secondly, from underwater photosynthesis carried out by plants and algae. 

Plants and algae can carry out photosynthesis during the day. At night, plants stop producing oxygen and instead consume it through respiration. That said, typically, the amount of oxygen entering the water exceeds what is used up by the oxygen-requiring processes such as fish respiration, microbial biological filtration and the natural breakdown of organic matter. Wild fish, in general, do not have difficulties getting enough oxygen in natural waters to support their metabolic needs. 

In backyard fish ponds, there is typically a higher density of plants, animals and microbes compared to natural water bodies. This can create a situation where oxygen is consumed faster than it can be replenished through photosynthesis and diffusion. It is known that low levels of dissolved oxygen and the length of low-oxygen conditions can impact fish in various ways, including reduced appetite, slow growth, greater susceptibility to disease, and in severe cases suffocation and death. 


Poor Aeration and Algae Blooms

Poor Aeration and Algae Blooms

In natural ponds, which are often deeper than backyard ponds, the oxygen level at the bottom of the pond can get very low (become anaerobic). This low-oxygen environment at the bottom of the pond allows the release of nutrients from decomposing organic matter that promote the growth of algae. 

In backyard ponds, a combination of poor water circulation, inadequate aeration, and the presence of sludge layer can create conditions that still favor unwanted algae blooms. When this happens, the oxygen levels in the backyard pond can decrease.

Effects of Low Oxygen on Fish Health

When goldfish and koi are exposed to low oxygen levels (below 2 ppm), their health is seriously compromised. 

Unfortunately, in backyard ponds, persistently reduced oxygen levels might go unnoticed. If this is the case, at first, fish will linger near the surface of the water and actively pump their gills. They might also eat less food than normally but they still swim around and appear generally well. 

Nonetheless, their immune system is not working 100% and therefore their ability to fight off diseases is dramatically reduced. There are many disease-causing organisms in backyard ponds that are typically kept in check by the fish’s immune system. Yet, prolonged exposure to low oxygen levels can make fish susceptible to infestation by parasites, bacterial disease or fungal infections. 


aeration methods

Mechanical Aeration Methods: Preventing Low Oxygen Conditions

To prevent low-oxygen problems, pondkeepers use mechanical aeration methods such as water pumps, fountains, and waterfalls to supplement the natural oxygen levels in backyard ponds. 

Let’s explore the following methods of aeration to maintain optimal oxygen levels in your goldfish, koi, and water garden.

Two Methods to Keep Your Pond Oxygenated

The movement of oxygen from the atmosphere primarily happens at the boundary between air and water (i.e. the surface of the pond). The larger the surface area of the pond the easier it is for oxygen to diffuse into the water. Given that backyard ponds are not as large as natural ponds, it is essential that we agitate (stir up) the surface to help the diffusion of oxygen into the water. 

As we discussed in another article, pond filters can perform dual duty by splashing the surface of the water. For example, it is known that an external filter that sends water to a waterfall is a great way to aerate the water. 

  • If you have a small pond, such as a whisky barrel, use a miniature submersible pump with a spitting frog, bird, or fountain head.

Practical Tips for Maximizing Oxygen Levels

  • Keep the aeration device running at all times! Oxygen levels rise and fall in a 24-hour period (photosynthesis by plants and algae during daytime and consumption of oxygen by the plants themselves at night) which is why it is crucial you do not turn off the aeration device at night or when you are away. This could otherwise very quickly lead to a drop in oxygen levels. 
  • Warmer water holds less dissolved oxygen! This is why it is important to regularly inspect and service the water pump, waterfall, fountain and other water circulation equipment, especially in the warmer summer months. 
  • Clogged prefilters and screens slow down water flow! Dirty impellers can even freeze up and stop pumping of the water altogether. Therefore, to maximize oxygen levels, regularly clean the water pump’s prefilters, screen and impellers. 
  • Maintain a reasonable fish population! Overstocking can lead to a significant increase in oxygen demand, which can put stress on the fish and compromise their health. 
  • Keep the pond clean! While your pond does not need to be as pristine as a swimming pool or spa, it is important to prevent heavy build-up of debris and oxygen-depleting sludge from settling at the bottom. 

Final Thoughts on Pond Aeration

  • Plants, fish, and microbes remove oxygen from pond water.
  • Backyard ponds need aeration to replenish oxygen used by aquatic life.
  • Low oxygen levels in ponds have a detrimental impact on the health of fish, resulting in increased susceptibility to diseases and various other health issues. 
  • Surface agitation from water movement transfers oxygen from the atmosphere to the water.
  • Use a water pump or air pump to keep the water agitated.
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