Causes & Dangers of Low Oxygen in Ponds

Properly aerating a pond is a seriously underappreciated method of ensuring ponds are clean, clear, and healthy. Aeration can prevent green water, it contributes to improved bacterial colonization in ponds and it helps to circulate the water to prevent stagnation; it is a vital part of maintaining a healthy pond and it’s why aeration is one of our 5 Tips Which Can Make A Big Difference To Your Pond.

Unless your pond has been specifically designed to control intensive fish culture, it may struggle to remain healthy. Professional, or experienced, pondkeepers will pay close attention to the location of the pond, the types of fish they keep, and the equipment in the pond to prevent problems and ensure the pond remains healthy. Other pondkeepers may not pay as close attention to these when a pond is being built, and it can potentially cause problems further down the line. Luckily, there are many ways in which you can aerate a pond.

Symptoms of Low Oxygen (Useful Blogs: Signs of Low Oxygen in Ponds)

The common symptoms of a lack of aeration include the below; if you see any of the below symptoms, you should investigate further. This may include testing your water with a Tetra Pond Test 6-in-1 or a Blagdon Pond Health Test Kit and visually check the fish for any signs of fish diseases.

• Fish gasping at the surface of the pond or at any entry points for water (Waterfalls, fountains, streams).
• Foul odours - decaying organic matter (Fish waste, plants, sludge) can indicate that there is a lack of oxygen, water movement or filtration.
• Rapid algae development - This can be a sign of poor aeration and filtration.

Causes of Low Oxygen (Useful Blogs: Temperature, Green Water and Slimy Algae, Fish Food, Filtration FAQs, Pond Sludge, Pond Plants)

We have tried to produce a easy, concise list of the reasons why your pond may suffer from low oxygen levels.
• Excess Sunlight – In the summer months, as the temperature increases, the metabolism of your fish will also increase. This means they will require more oxygen. You may start to see your fish go sluggish as they conserve energy or your fish may be crowded around an entry point of water (waterfalls, open hoses etc) as they seek out extra oxygen; so keep an eye on the activity of your fish.
• Overcrowding – In short, fish require an aerated pond to thrive and remain healthy. Increasing the number of fish in the pond will decrease the amount of oxygen in the pond, which can then affect the chemicals in the pond and lead to sludge. In turn, this fuels green water and other common pond problems. The green water (caused by simple algae) can block sunlight penetrating the depths of the pond, which will stop the production of oxygen by your plants.
• Excess Food – Too much food in the pond can cause excess sludge to build up from the decaying leftovers. As above, this can increase the harmful chemicals in the pond and lead to green water and a decrease in healthy bacteria in your pond.
• Lack of pumps or aerators relative to water volume – Having no dedicated aerators in your pond is a very dangerous thing to do, especially in larger ponds and especially if your location is prone to high temperatures. An aerator is a small mechanical machine which pumps air into your pond; they are the best form of aeration your pond can get and certainly worth purchasing.
• Inefficient Equipment – If you only have a small aerator, or a pump & filter set that is too small for the volume of your pond, this could be causing low oxygen levels. A small aerator might not be pumping enough oxygen into your pond and a small pump & filter set might not be removing enough sludge.
• Decaying materials – As above, decaying organic materials in your pond will form sludge, which can cause other problems. While uneaten fish food is the main culprit, this can also include decaying leaves, plant trimmings or other organic material. It’s best to locate your pond away from trees, regularly trim your plants and use a skimmer net or cover net to remove debris and stop any organic material from entering your pond.
• Lack of pond plants – A lack of plants in your pond is a big problem; we always encourage people to cover at least 50% of the pond in plants. This is because they help to provide oxygen, filtration, and shelter for your fish. They also help to make your pond look interesting and a real centrepiece of the garden!

How to improve Oxygen levels (Useful Blogs: How to Oxygenate a Pond)

Aerating a pond doesn't include a lot of hard work; it can be easy. As above, we have listed a few common methods to aerate your pond.
• Air Pumps - These are mechanical pumps which push air into the deeper parts of your pond. The air is then diffused where it enters, allowing the air to dissolve much more efficiently. 
• Pond Plants - Plants are critical to pond health. You should aim to cover at least 50% of your pond in plants. As above, pond plants provide oxygen, filtration, and shelter for your fish. 
• Provide Shade - Adding shade to your pond will help to reduce the temperature of the water. This helps to increase the dissolved oxygen rate; meaning there is more oxygen available for your fish. This is commonly done via canopies or floating plants (like the the Moerings Floating Pond Planter with Three Pond Plants).
• Waterfalls / Fountains - An easy way to aerate your pond is through water movement and splashing; the disruption to the water helps to capture oxygen and let it dissolve naturally into the pond. By circulating the water from the bottom of the pond, you are helping to ensure efficient aeration. They are also beautiful centre pieces and great for every pond, regardless of function.

You may also find the below blogs useful:
• Aeration Blogs
• Pond Problems Blogs
• Pond Plants Blogs
• Top Tips Blogs
• Water Features Blogs

If you have any queries, please email us on info@pondkeeper.co.uk.