What Causes Algae in Ponds and Lakes?

What Causes Algae in Ponds and Lakes?

Are you struggling with algae growth in your pond or outdoor water feature? Learn the causes and how to get rid of algae once and for all!

Algae – the bane of every pond and water feature owner's existence. Those unsightly green, brown, or even red smears on the water's surface can quickly turn a beautiful pond into an eyesore. 

Not only is algae aesthetically displeasing, but it can also disrupt the delicate ecosystem of water features – causing everything from foul odors to decreased oxygen levels and even potential harm to fish and plant life. 

As frustrating as algae can be, knowing what causes these blooms continues to be the first step in regaining control over your aquatic paradise. And once you know how to treat your water feature to prevent algae growth, you'll never have to deal with it again.

So why does algae grow in your water feature? To understand why, we need to go back to the what of algae itself.

What is Algae?

Also known as cyanobacteria, blue-green algae is a type of microorganism that can be found in both freshwater and saltwater environments. It thrives in warm, nutrient-rich water and is typically green or blue in color.

Algae can reproduce rapidly – forming dense mats on the surface of the water. You’ve probably noticed them more in the summer months when water temperatures are warmer and sunlight is more abundant. This is because algae photosynthesize – they use the sun's energy to produce their own food, like plants do.

How Does Algae Grow?

But why does this rapid growth happen? To put it simply, nutrients. Algae need a steady supply of nutrients, such as nitrogen and phosphorus, to thrive. These nutrients can come from various sources like decaying leaves or fish waste. When there’s an excess of these nutrients in your water feature, whether from overfeeding fish or having too many plants, algae will flourish.


Sunlight also plays a crucial role in algae growth. As mentioned before, algae rely on photosynthesis for survival and sunlight is a key component in this process. The longer days and stronger sunlight during the warmer months provide optimum conditions for algae to grow quickly.

Water Temperature

Along with sunlight, warmer water temperatures can contribute to algae growth. Algae thrive in warm water, with the ideal temperature range being between 75-85 degrees. 

This is why you may notice more algae growth in your pond or aquarium during the summer months when water temperatures are at their peak. And once the algae begin to grow, they can quickly take over the entire body of water if not properly managed.

Nutrient Levels

Algae require nutrients in order to grow and reproduce. These nutrients come from a variety of sources such as decaying organic matter, fish waste, and fertilizers used in nearby gardens or lawns. 

If these nutrient levels are too high, they can lead to excessive algae growth – which is why it’s important to regularly test the water quality in your pond to keep nutrient levels in a healthy range.

How Do You Get Rid of Algae?

Once you know how algae thrive, you can start to take steps to prevent and control their growth. Here are some methods to get rid of algae in your pond or aquarium:

1. Manual Removal

The first step in controlling algae is to manually remove as much of it as possible. Use a net or rake to skim the surface of the water and remove any visible algae. This will help reduce the overall population of algae and make it easier for other methods to be effective.

Manual removal can be time-consuming, but it is an important first step in controlling algae growth. A great way to make this task easier is to invest in a pond vacuum, which can quickly and efficiently remove algae from the bottom of your pond or aquarium.

2. Reduce Nutrient Levels

As mentioned before, algae thrive on nutrients such as nitrogen and phosphorus. By reducing these levels in your water, you can limit the growth of algae. One way to do this is by using aquatic plants, which absorb excess nutrients and compete with algae for resources.

You can also limit the amount of organic matter in your water by regularly cleaning filters and removing any debris from the bottom of your pond or aquarium. A pond filtration system or UV sterilizer can also help to keep nutrient levels in check.

3. Add Beneficial Bacteria

Fight plants with other living organisms? It may sound counterintuitive, but adding beneficial bacteria to your pond or aquarium can actually help control algae growth. 

These bacteria consume excess nutrients and compete with algae for resources. They also help break down waste products, keeping the water cleaner and less hospitable for algae to thrive.

Beneficial bacteria can be found in specialized products such as biological filters or additives that can be added directly to the water. Adding a handful of natural materials like barley straw or lava rocks to your pond can also introduce beneficial bacteria.

4. Reduce Sunlight Exposure

It may seem silly to reduce sunlight in an outdoor setting, but one key to controlling algae growth is limiting its access to light. Algae need sunlight to perform photosynthesis and grow, so by reducing the amount of direct sunlight in your pond or aquarium, you can limit their growth.

Here are a few ideas to help you reduce sun exposure to your pond while still maintaining the look and feel of a natural environment:

  • Plant shade-providing plants like water lilies, lotus, or cattails in and around your pond.
  • Use floating plants like duckweed or water lettuce to create a canopy over the surface of the water.
  • Install an awning or pergola over your pond to provide some shade during the hottest parts of the day.

5. Implement Aeration

Aeration is the process of increasing oxygen levels in your water. By introducing a constant flow of oxygen into your pond, you can help maintain a healthy balance of beneficial bacteria and discourage the growth of harmful algae.

You can install a pond aerator, which uses a pump to circulate water and add oxygen through a diffuser. Another option is to add a waterfall or fountain feature that will also help increase oxygen levels.

Can Algae Be Helpful To A Pond?

It’s not all bad news when it comes to algae. In fact, some types of algae can actually be beneficial to your pond. These include filamentous algae – which can provide food and shelter for aquatic insects and small fish.

Other types of algae, such as diatoms and green water algae, are important sources of food for many aquatic organisms. As long as these algae are kept in balance by proper maintenance and control methods, they can contribute to a healthy ecosystem within your pond.

Keep Algae Away For Good with Living Water Aeration

If you want to keep your pond or outdoor water environment clean of pesky algae, you may want to consider investing in the right methods and equipment. 

At Living Water Aeration, our team of experts can help you find the perfect solution for your specific needs. We offer a wide range of aeration equipment and water treatment products designed to keep algae growth under control.

Stop algae once and for all with a premier water aeration system from Living Water Aeration. Visit us online to learn more – and make sure to visit our blog for more great pond maintenance and care insights! 

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