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Best Pond Algaecide & Pond Algae Killer in 2021 (Safe for Fish)

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Pond algaecide is extremely effective at killing algae in ponds.

And it kills all kinds of algae, including the more troublesome string and blanketweed algae, extremely fast!

But… algaecides can also be bad for your pond’s fish and ecosystem.

With that in mind, let’s look at the best pond algaecide products on the market today, how to apply them for best results, and cover some frequently asked questions.

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Product Comparison Chart

Description Algae Types Price
GreenClean Algaecide GreenClean Algaecide All forms of algae (best for string and blue/green algae) SEE PRICE »
Cutrine Plus Algaecide Cutrine Plus Algaecide All forms of algae SEE PRICE »
API Pond ALGAEFIX Algae Control API Pond ALGAEFIX Algae Control Green water, string or hair algae, and blanketweed SEE PRICE »
Microbe-Lift Algaway 5.4 Algaecide Microbe-Lift Algaway 5.4 Algaecide Green water, string or hair algae, and blanketweed SEE PRICE »

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Best Algaecide For Ponds

Pond algaecides come in different types, use different ingredients, and some are meant for only specific types of algae. Let’s review the four best pond algaecide products to find the one that’s best for your pond and situation.

GreenClean Algaecide

GreenClean is a granular algaecide that works especially well string algae (though it should work for all forms). It breaks down algae cells on contact through the power of oxidation, and you’ll even see results in as little as 24 to 48 hours!

This product is free from any harsh chemicals such as chlorine, copper, and phosphate-free. And like all the algaecides in our list, GreenClean is EPA approved and safe for fish and plants when used according to the manufacturer’s directions.

If your pond or lake suffers from string or blue/green algae, then GreenClean is going to be your best bet.

Specifications

Eliminates: All forms of algae, but designed for string algae and blue-green algae
Active Ingredients: Sodium Carbonate Peroxyhydrate – 42.5%
Fish Safe: Yes
EPA Registered: Yes

GreenClean Algaecide

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GreenClean Algaecide

Cutrine Plus Algaecide

Cutrine Plus is a professional grade algaecide used for small backyard ponds up to larger farm ponds, lakes, reservoirs, hatcheries and more.

Cutrine Plus is perfect for algae of all types and works fast, within 1 to 2 days. Plus, it contains chelated copper which is designed to help control algae for well after it’s applied.

It’s safe for koi, goldfish, and trout as long as the water hardness is less than 50PPM (You can check with a pond water test kit). You can even fish, swim, and/or drink water immediately after treating with this product!

Specifications

Eliminates: All forms of algae, including planktonic, filamentous, and chara
Active Ingredients: Copper Ethanolamine Complex – 27.9%
Fish Safe: Yes
EPA Registered: Yes

Cutrine Plus Algaecide

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Cutrine Plus Algaecide

API Pond ALGAEFIX Algae Control

API Pond ALGAEFIX will help control the most popular types of pond algae including green or green water algae, string or hair algae, and blanketweed.

ALGAEFIX pond treatment is registered with the EPA and is safe for fish and live plants in ponds.

When using this product (and most other algaecides), be sure you have proper aeration setup to avoid fish kills from oxygen deprivation.

Specifications

Eliminates: Green water algae, string or hair algae, and blanketweed
Active Ingredients: dimethyliminoethylene dichloride, ethoxylate – 4.5%
Fish Safe: Yes
EPA Registered: Yes

API POND ALGAEFIX Algae Control Solution

API POND ALGAEFIX Algae Control Solution

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Microbe-Lift Algaway 5.4 Algaecide

Microbe-Lift Algaway 5.4 Algaecide was designed to remove many types of algae from ponds and water fountains and improve the water quality.

This pond algae killer is EPA registered and is safe for fish and pond plants as long as you follow the directions. Just be sure, if you have a koi or fish pond, to have proper water aeration setup to avoid fish kills from oxygen deprivation.

A 1 gallon bottle will treat up to 45,424 gallons of pond water.

Specifications

Eliminates: Green water algae, string or hair algae, and blanketweed
Active Ingredients: Poly[Oxyethylene (Dimethyliminio) Ethylene (Dimethyliminio) Ethylene Dichloride] – 5.4%
Fish Safe: Yes
EPA Registered: Yes

Microbe-Lift Algaway 5.4 Algaecide

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Microbe-Lift Algaway 5.4 Algaecide

How To Use A Pond Algaecide For Best Results

To help ensure you don’t run into any of the negative effects of using an algaecide in your pond, here are our “best practices” to follow so you get the best results.

  • Follow the Product Directions
    First and foremost, ALWAYS follow the directions on the product package exactly as described. This should be obvious, but not following the directions exactly, whether you meant to or not, can lead to fish kills and other issues with your pond. Be mindful of each step and double-check your doses before adding them to your pond.
  • Proper Pond Aeration
    To maintain adequate oxygen levels in your pond during treatments, you’ll definitely want to make sure you are running an aerator. Especially if you have fish in your pond. You can add an air pump to pump oxygen directly into the water, or add a fountain, a pond spitter, or a waterfall to help oxygenate the water.

    AirPro Pond Aerator Kit by Living Water

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    AirPro Pond Aerator Kit by Living Water
  • Treat Your Pond In Sections
    Whenever you use any chemical products in your pond, it’s a good idea to treat it in small sections. This is a popular practice when trying to get rid of pond weeds, as well. By treating in sections, you’ll effectively reduce the chances of overtreating your pond with algaecide and it will help keep the water oxygen levels within an acceptable range.
  • Remove Dead Algae
    Algaecide is extremely effective at killing algae in pond water. And it works really fast! The bad news is that the dead algae will just sink to the bottom of your pond, adding to your pond’s sludge problem and increasing the number of harmful chemicals like ammonia and nitrites in your pond. To make matters worse, those harmful chemicals also fuel the growth of new algae! The easiest ways to clean up the dead algae are with a pond vacuum or a pond rake.

    Oase Pondovac 5 Pond Vacuum Cleaner

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    Oase Pondovac 5
  • Keep Your Pond Filter Clean
    The algae that don’t sink to the floor of your pond, will end up in your pond filtration system. While this is a good thing, if you have a lot of dead algae getting pumped into your filter, it will get clogged up very quickly. So, be sure to check and clean your filter often when using algaecides.

What Is The Best Treatment For Pond Algae?

Algaecides are extremely effective at killing algae in your pond. But… (there’s always a but)

It’s not necessarily the best treatment. Resorting to using pond chemicals for algae should be more of a last resort. We highly recommend you check out our guide on Pond Algae Control! We detail all the steps you should take to get rid of pond algae like a pro, with many of them being natural remedies (that actually work). Within that guide, in most cases, will be the best pond algae treatment for your pond or water garden.

Now, with all that said, if you’ve exhausted all your other options including the natural remedies in our Pond Algae Control guide, a chemical might be the only thing that works to get rid of (and help control) your algae problem. In that case, an algaecide treatment is the best option.

Pond Chemicals FAQ

What chemical kills algae in ponds?

Algaecide is a chemical that kills algae in ponds. The active ingredients in algaecides will depend on the product. They are extremely effective at killing algae of all types in ponds. However, anytime you use a chemical in a pond it should be used with caution and according to the manufacturer’s directions.

How does algaecide kill algae?

Most of the commonly used algaecides on the market work in the same manner, they attack and kill the cells of algae on direct contact. This is an extremely quick process and is why they are so effective and fast-acting. Keep in mind that these dead algae just don’t disappear. They instead sink to the floor of your pond and clog up your pond filter, and essentially leading to a depletion in oxygen levels. This is why we recommend manually cleaning up the dead algae.

Can algaecide kill fish?

Most popular pond algaecide products are marketed as being fish-friendly as long as you follow the directions exactly as described on the products label. Just keep in mind, that while this may be true, often it isn’t the product that directly harms or kills fish, rather it’s the effects of a rapid algae die-off.

These rapid die-offs can lead to depleted oxygen levels in your pond, which can be fatal to fish, especially if you have a lot of fish in your pond or water garden all competing for oxygen. Proper aeration is a must when using an algaecide in a pond with koi or other pond fish.

Can pool algaecide be used in a pond?

I have seen algaecide products marketed for pond, pool, and fountain use. However, I would not use a pool algaecide in a fish or koi pond unless it specifically states it’s safe for fish and aquatic life. It’s simply not worth it. Preferably, choose one of the recommended pond algaecides from above and follow the directions on the package.

Is Pond Boss Algaecide safe for fish?

Yes, Pond Boss Algaecide is EPA registered and won't harm fish, pond plants, or other aquatic life if used as directed. As discussed above, it’s not usually the algaecide itself that harms aquatic life, but the oxygen depletion that can occur. So, be sure to have an adequate pond aerator running during this process.