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How to Prevent, Treat and Control Pond Algae

How to Prevent, Treat and Control Pond Algae

Algae, the unsightly green stuff that grows in our ponds from time to time. It's one of the most common issues pond owners face.

All ponds will eventually come across this issue. We can help you keep it at bay, but first, we need to understand it.

In Canada, we have 2 main types of algae that form, Green Water Algae (suspended algae) and String Algae. We'll be focusing on these two types. If you haven't already, you'll want to learn what these two algae's are and what causes them. This important knowledge will help you beat your algae issues and keep them away.

To learn more about what pond algae is and what causes it, click HERE

We'll be going over how you can prevent algae before it forms as well as how to control it and get rid of it once it does form. Algae can be an annoying sight that goes away after some time or a continuous issue, following these steps will help rid your pond of it faster and help keep it away.

Control and Prevention for Both Types of Algae

Control and prevention is the best thing you can do for a pond. Once algae starts forming you can still get rid of it fairly easy; however, once its a major issue, it can take great lengths and effort to get rid of it. The best method is prevention.

Both Algae forms are relatively similar so we'll start with some things you can do to control and prevent both of them. If you already have algae issues, you should review the prevention section as well and take the appropriate measures and treatments available.

Since the two main factors to algae growth are 1. Excess nutrients and 2. Direct Sunlight, we'll want to control these issues no matter where we are in the prevention or control timeline.


Limit the Amount of Fish in Your Pond

Pond fish such as Koi and Goldfish, tend to be larger than aquarium fish, as such we don't follow the same rules as we would an aquarium. A pond should have no more than 1 inch of fish per 10 gallons of water.

Let's say you have a pond that holds 1000 gallons of water, you would want no more than 100 inches of fish. This could mean only 3-4 Koi or 5-7 Goldfish if they are fully grown. Koi grow 24 - 36 inches and Goldfish can grow up to 15 inches fully grown.

Control Fish Feeding

Fish food breaks down quickly, causing water imbalances. As such, we need to ensure we are only feeding fish the amount they need. To solve this issue, there are fish foods that don't break down the same as others or cause cloudy water. These foods can help. Also make sure you follow the feeding instructions and don't overfeed fish. A general rule of thumb is to feed the fish only what they can eat in 4-5 minutes, then remove the rest of the uneaten food with a net.

Add Some Shade

Since direct sunlight is a cause of algae, we can try minimize this issue or remove it completely. Adding a large tree around the pond to help block some sunlight is one way to reduce direct sunlight on the pond, just ensure any falling leaves are removed from the pond before they decay.

Another shade option is water cover plants such as lilies or lotus'. These plants cover the surface of the water which limits the sunlight's penetration into the water. In turn this reduces the risk of algae. We recommend up to 2/3 of the pond covered in pond plants.

Add Aquatic Plants

Aquatic plants used to help prevent algae

Aquatic plants are a great way to remove excess nutrients in your pond. The plants consume the nutrients and clean the water. You'll want to make sure the plant roots are either planted directly into the pond substrate or into pond planting media. They should not be planted in a typical potting soil as there are too many nutrients that will cause further issues.

Control What Goes in Your Pond

Controlling what goes into your pond is a great way to reduce the risk of algae and also help get rid of it if it does form.

Things to look out for and remove or deter:

  • Animals urinating - Causes water imbalances. Dogs, deer, etc.

  • Frog, turtle and fish waste - Too many fish, reptiles or amphibians in the pond

  • Bird waste - Fecal matter in the water causes issues, geese are a major issue around here

  • Leaves and debris - Remove with net asap so they don't decay

  • Fertilizer and lawn runoff - Added nutrients cause water imbalances