Winning The Battle Against Algae: Koi Pond Algae Control

Small pond overtaken by green algae

Ever looked at your koi pond and wondered why it’s not as clear as it used to be? Or perhaps you’ve noticed a greenish tinge that wasn’t there before?

If so, you’re not alone. Algae is a common issue for koi pond owners, but the good news is that it can be controlled.

In this blog post, we’ll explore the pros and cons of chemical and biological treatments for koi pond algae control in koi ponds. By the end, you’ll have a clear understanding of how to maintain a healthy, algae-free pond (though the best method for koi ponds in North Augusta is regular pond cleaning and maintenance).

Chemical Treatments For Koi Pond Algae Control

Large and beautiful low maintenance pond

When It Is & Isn’t Safe To Use Chemical Treatments To Control Algae In Koi Ponds

Chemical treatments can be highly effective in controlling algae growth, but they must be used responsibly.

Overuse or incorrect use of chemical treatments can harm or even kill your fish. Always follow the manufacturer’s instructions when it comes to dosage, and consider seeking professional advice if you’re unsure.


Chemical control typically involves the use of algaecides, which can kill or inhibit all types of algae.

These chemicals, including products containing simazine, chelated copper, or potassium permanganate, work best as a preventative measure. However, caution must be exercised when using an algaecide, as overdosing can harm or even kill your fish.

It’s best to select from fish-safe algaecide products.

Copper Compounds

Copper compounds are another chemical method used to control algae.

They are effective against many types of algae but should be used with caution as they can be toxic to fish and other aquatic life if used improperly.

Hydrogen Peroxide

Hydrogen peroxide is a powerful oxidizer that can effectively kill algae. However, it must be used carefully as it can also harm fish and beneficial bacteria in the pond.


Diquats are a type of herbicide that can be used to control algae.

They work by disrupting the process of photosynthesis, effectively starving the algae. However, they can also harm non-target plants and should be used with caution.


Pond dyes can help control algae by blocking sunlight, thus inhibiting photosynthesis. They are generally safe for fish and plants but can stain anything they come into contact with.


Binders, also known as phosphorus binders, work by binding to the phosphates in the water, which are a key nutrient for algae.

By reducing the amount of available phosphates, binders can help control algae growth. However, they do not kill existing algae and should be used as part of a comprehensive algae control strategy.

Flocculants For Water Clarity

If your pond water is cloudy, a flocculant may be necessary to clear it up.

Flocculants work by binding small particles in the water, causing them to clump together and settle at the bottom of the pond. This process can help clear up cloudy or murky pond water, improving the overall water quality, which can help with koi pond algae control.

Pros And Cons Of Chemical Koi Pond Treatments

Pros Of Chemical Treatments

  • Effectiveness: Chemical treatments can be highly effective at controlling algae, often providing quicker results than biological methods.
  • Broad Spectrum: Many chemical treatments can target a wide range of algae species.
  • Preventative Action: Some chemicals can prevent the growth of algae when used regularly and correctly.

Cons Of Chemical Treatments

  • Potential Harm To Aquatic Life: If not used correctly, chemical treatments can harm or even kill fish and other aquatic life.
  • Temporary Solution: Chemical treatments often address the symptoms (algae growth) without addressing the underlying cause (excess nutrients).
  • Possible Resistance: Over time, algae may develop resistance to certain chemical treatments, reducing their effectiveness.

Biological Treatments For Koi Pond Algae Control

Beautifully clean and clear koi pond thanks to pond maintenance methods

Natural Balance And Biological Competition

To control algae naturally, we must limit sunlight and nutrients.

Algae require sunlight, so deep ponds are preferable in well-lit gardens. Sheltering your pond from sunlight will make algae growth much easier to control.

Nutrients need to be removed from the pond, or algae problems will occur.

The pond must also have good circulation throughout to sweep debris to the drains.

Beneficial Bacteria

Beneficial bacteria play a crucial role in maintaining a healthy koi pond ecosystem. These bacteria help break down organic matter and convert harmful compounds like ammonia and nitrite into less harmful compounds.

Aquatic Plants

Aquatic plants can help control algae by competing for the same nutrients that algae need to grow. By adding aquatic plants to your pond, you can reduce the amount of available nutrients for algae, thereby limiting their growth.

Aquatic plants also provide shade for your pond. This prevents algae from getting the sunlight it needs to grow.

Koi Fish

Koi fish can contribute to their own koi pond algae control by feeding on certain types of algae and organic matter that could otherwise contribute to algae growth.

However, koi also produce waste that can increase nutrient levels in the pond, so a balance must be maintained.

Rocks And Gravel

Rocks and gravel provide a surface for beneficial bacteria to grow.

These bacteria can help prevent algae growth by consuming excess nutrients in the water. However, they can also trap organic matter, which can decompose and increase nutrient levels, so regular cleaning is necessary.

Discover the differences between DIY and professional pond cleanings.

Wetland Filter

A wetland filter, or a constructed wetland, can be an effective biological treatment for algae control.

It works by mimicking natural processes to filter the water, using plants and beneficial bacteria to remove excess nutrients that can fuel algae growth.

More Mechanical Filters

Filters are essential for pond health. Additional mechanical filters can be used to physically remove algae and other particles from the water.

These can include sponge filters, bead filters, and sand filters. The choice of filter will depend on the specific needs of your pond.

Barley Straw

Barley straw has been used for centuries to control algae growth.

As it decomposes, it releases compounds that inhibit the growth of algae. However, the effectiveness of barley straw can vary, and it may not be suitable for all ponds.

Ultraviolet Systems

Ultraviolet systems can effectively kill planktonic algae.

These units are quickly becoming a standard item in conjunction with an adequate filter system. A UV light will speed up the balancing of the pond ecosystem significantly, reducing the need for other forms of koi pond algae control.

Pros And Cons Of Biological Koi Pond Treatments

Pros Of Biological Treatments

  • Natural Balance: Biological treatments work with nature, not against it, helping to maintain the natural balance of the pond ecosystem.
  • Safe For Aquatic Life: Biological methods are generally safe for fish and other aquatic life.
  • Long-Term Solution: By addressing the root causes of algae growth, such as excess nutrients, biological treatments can provide a long-term solution to algae problems.

Cons Of Biological Treatments

  • Slower Results: Biological treatments often take longer to show results compared to chemical methods.
  • Requires Regular Maintenance: Many biological treatments, such as the use of beneficial bacteria or aquatic plants, require following a koi pond maintenance routine to remain effective.
  • May Not Be Effective Against All Types of Algae: Some types of algae may not be effectively controlled by biological methods alone, requiring the use of additional treatments.

Understanding Algae In Ponds

String algae from a koi pond on a stick

Types Of Algae

There are two main types of algae that can plague your koi pond: green algae and string algae.

Green algae are microscopic, single-celled organisms that float in the water, giving it a greenish hue. This green water is unsightly and can cause a weird smell.

On the other hand, string algae (also called filamentous algae), true to its name, grows in long strands that cling to rocks, waterfalls, and other surfaces in your water feature.

Factors Contributing To Algae Growth

Several factors can contribute to algae blooms in your pond:

  • High light levels and elevated temperatures provide the perfect environment for algae to thrive.
  • Still water and poor water circulation can also lead to an overgrowth of algae.
  • Excess nutrients, particularly nitrates and phosphates, act as a fertilizer for algae.
  • High pH or alkaline water can also promote algae growth.

Achieving A Healthy Koi Pond

Large koi pond with tall waterfall and aquatic plants

Both chemical and biological treatments have their place in maintaining a healthy koi pond.

The key is to understand the specific needs of your pond and to apply the right combination of treatments to achieve a healthy and thriving koi pond. Regular maintenance and monitoring are essential to prevent and address any issues promptly.

Find out the cost of koi pond maintenance in Augusta, GA.

Control Alage In Your Koi Pond With Amen Corner Ponds

You’ve learned about the types of algae that can invade your pond, the factors that contribute to their growth, and the chemical and biological treatments available to control them.

But what’s the next step?

Many people choose Amen Corner Ponds to help. We offer high-quality pond cleaning and pond maintenance services that can help keep your pond in top shape. Our team of experts understands the unique challenges of algae control and can provide the right solutions tailored to your pond’s needs.

Don’t let algae take over your beautiful koi pond. Take action today to ensure your pond remains a vibrant and healthy habitat for your koi. Fill out our contact form today, or give us a call. Your koi will thank you!