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The 11 Best Pond Algaecides & Algae Killers

Algal blooms are a fact of life for every pond, whether it is a small residential pond or a large agricultural pond.

Algal blooms are a nuisance to every pond owner, whether they turn the water green or coat the surface with a slimy film. The faster the algae is cleaned, the better.

Fish ponds present a particular challenge when considering algae control measures because it is important to protect the aquatic life there.

Fortunately, there are treatments that can eradicate the algae in the pond without killing the fish in the process.

When used correctly, the algaecides that BestForPets (bestforpets.org) reviews here are completely harmless to fish.

Hopefully, you will be able to discover the best pond algaecides & algae killers that can restore clarity to your pond by evaluating these options.

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icon Reviewed & Fact - Checked by

Deborah R. Fletcher (DVM)


The information provided is current and up-to-date, in line with the latest research conducted in the field of veterinary medicine.

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Top Pick: API Pond Algaefix


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  • Types of Green Algae, String Algae, and Blanketweed That It Is Effective Against
  • 4.5% Dimethylimino ethylene dichloride ethoxylate, the active ingredient.
  • Toxin-free for aquatic life and plant life

API Pond Algaefix is the greatest pond algaecide and algal killer overall, in our opinion. This API liquid algaecide works quickly and efficiently against widespread pond algae.

This algaecide is fish-friendly, but only if used properly. You should know the complete capacity of your pond before adding any product. In order to keep your pond from decomposing after applying chemical algaecides, you should install some sort of aeration system.

Fish are at risk when oxygen levels drop because of the widespread death of algae. API Pond Algaefix may be used to both eradicate a current algae bloom and prevent more blooms from occurring.

The speed with which this solution kills algae is a strong selling factor, however a really large infestation may take longer to eradicate.


  • A fast and efficient method of killing specific types of algae
  • Aids in avoiding further epidemics
  • Competitively priced


  • Crustaceans like shrimp and crabs should avoid it.
  • Significant algal growth reduces effectiveness.
  • Doesn’t work on all algae

The Most Cost-Effective Tetra Algae Pond Block

Tetra Pond Block 4 Count, Controls Algae Growth In Ornamental Fish Ponds

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  • Types of Algae It Is Effective Against: Green Algae, String Algae
  • Copper sulfate and diuron are the two main active ingredients.
  • Marine life-friendly.

Although it may only be used in backyard or decorative ponds, the Tetra Pond Block is one of the most cost-effective algaecides available.

When compared to the other items on this list, this one is both cheap and straightforward. Unfortunately, this product is not suitable for use with living plants and is limited to usage in man-made ponds.

Although it has some restrictions, the Pond Block may be used to successfully remove algae from fountains and ponds used for decorative purposes.

This algae killer is cost-effective since its slow-dissolving blocks keep working to prevent algae growth for up to 30 days. Make sure your pond has adequate aeration and follow the guidelines to the letter.


  • Inexpensive
  • Long-lasting
  • It works well in fountains and ponds for aesthetic purposes.


  • Decorative water features alone.
  • Definitely not a place for plant life.

Pure and Natural Granular Algaecide, Top of the Line

BioSafe Systems 3002-8 GreenClean Granular Algaecide String Algae Control

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  • The product is marketed specifically for string algae, however it is equally effective against blue and green algae.
  • Sodium carbonate peroxyhydrate, the key ingredient.
  • Fish and plants may rest easy.

Green Clean Granular Algaecide is one of the most effective algaecides available, killing algal instantly upon contact. This treatment will destroy all types of algae, however it works particularly effectively on string algae.

You’ll need to be prepared to remove dead algae from your pond promptly after using Green Clean, before it settles and begins to disintegrate.

Fish in your pond might die if there are too few oxygen molecules because of excessive algal decay. It’s crucial that you constantly aerate your pond. If you’re worried about poisoning your pond with chemicals, this solution is a safe alternative. Algae cells are instantly degraded by Green Clean’s antimicrobial formula.


  • Toxic to algae on touch
  • Incredibly simple to use
  • lacks potentially harmful additives


  • Waste from dead algae must be removed immediately.
  • The formula is specific to string algae, although it is effective against other types of algae as well.

Algaecide 5.4 Microbe-Raising Algaway

MICROBE-LIFT ALGA32 Algaway 5.4 Algae Control Treatment

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  • Specifically Targeted Algae Species: Green Water Algae, String/Hair Algae, and Blanketweed
  • The Ethylene Dichloride and Polyethylene that Make It Work
  • Fish and plants may rest easy.

A liquid algaecide, Microbe-Lift Algaway is effective against the most common pond algae. Following the instructions, this product shouldn’t harm the majority of your pond’s fish or its vegetation.

Algaway may be used in ponds with koi and goldfish without harm, but you should make sure the water is well-oxygenated beforehand. Decomposing algae reduce water oxygen levels, therefore if you have a significant infestation, raking and removing part of the algae before applying the algaecide is suggested to prevent harm to your fish.

The process of killing algae with this product may take longer than with others, and it may require more than one application.


  • Eliminates huge algal blooms
  • Functionally simple


  • If misused, it poses a threat to aquatic life.

A Method for Treating Water in Tetraponds to Prevent Algal Blooms

Tetra 77188 Algae Control Treats

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  • Specifically Targeted Algae Species: Green Water Algae, String/Hair Algae, and Blanketweed
  • The Ethylene Dichloride and Polyethylene that Make It Work
  • Fish and plants may rest easy.

Tetrapond also offers an Algae Control Water Treatment that is plant-friendly and effective for both big and small ponds. The product comes in a concentrated liquid form that needs to be watered down before usage.

Since it is concentrated, a single bottle may treat a sizable pond. By decomposing algae cells, AlgaeControl eliminates the problem, although it takes longer to do so than Green Clean.

As much as three days may pass before you learn if more therapy is necessary. You’ll want to dilute this product properly and use just the perfect amount for your pond if you’re going to use it.


  • Effectively eradicates all prevalent pond algae
  • Economical for huge bodies of water


  • Dilution is required.

Granular Algaecide from Aquascape called EcoBlast

Aquascape 29311 EcoBlast Pond Algaecide

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  • Specifically, it eliminates green water algae, string algae, and hair algae.
  • Sodium carbonate peroxyhydrate, the key ingredient.
  • Fish and plants may rest easy.

The algae-killing properties of Aquascape EcoBlast are similar to those of other products in the same category. Granular rather than liquid, this solution is ideal for spot treatment of algae.

Aquascape, unlike some other algaecides, does not serve as a prophylactic measure. Despite its effectiveness, it often results in a rapid resurgence of the algae it kills.

You may also need to utilize the company’s other products, such as those for pond health maintenance and algae prevention. EcoBlast is functional across a wide range of water temperatures and pH values.

If you have a serious problem with string algae, you may need to rake and remove part of the algae before using this solution.


  • Work well in a variety of water conditions, including those with varying temperatures and acidity levels.
  • Incredibly simple to use
  • Very efficient


  • Not very effective in preventing algae growth.
  • Possible decreased efficacy in the face of widespread string algae blooms.

Pure D-solv Algae Crystals

CrystalClear Algae D-Solv Pond Algae Control

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  • Specifically Targeted Algae Species: Green Water Algae, String/Hair Algae, and Blanketweed
  • The Ethylene Dichloride and Polyethylene that Make It Work
  • Toxin-free; no harm will come to fish, plants, or wildlife

Pure as the driven snow If applied properly, Algae D-solv can eradicate algae growth quickly without harming pond vegetation or fish.

When an outbreak of algae occurs, you can use this product, but it shouldn’t be utilized to keep the pond healthy in the long run. As an added bonus, Algae D-solve is one of the few algaecides that guarantees to be harmless to any animals that could use your pond as a water source.

If you’re using a chemical algae killer, follow the manufacturer’s dosage instructions to keep your fish and plants safe. Check and clean your pond’s filters often when using Algal D-Solv since the rapid algae death it causes might lead to filter clogging.


  • Fast-acting
  • Non-toxic to fish and plants as well as other animals


  • Treatment cycles may need to be extended.

Pondcare API Microbial Algae Clean Green Water Biological Inhibitor


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  • Types of Algae It Is Effective Against: Green Water Algae
  • Specifically, Bacillus bacteria are the active ingredients.
  • Fish and plants may rest easy.

Chemical algaecides may be the quickest solution, but API Pondcare provides an option for individuals who are concerned about introducing any chemicals to their ponds.

This device eliminates the need for the use of harmful chemicals in aquatic environments by employing microorganisms that consume green water algae.

Not being a chemical means it may take longer to function and regular additions will be needed to a pond to keep algae under check. Green water is the only form of algae that Pondcare can successfully treat.

The product’s key selling point is that it is an all-natural algae treatment that won’t harm the aquatic ecosystem.


  • Zero chemical
  • Will not disrupt the delicate balance of the pond’s environment.


  • Specifically targets green algae.

Water Purification using Barley and Peat Extract in a Tetrapond

TetraPond Barley and Peat Extract For Naturally Clear Water

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  • It eliminates green water algae and aids in the prevention of string algae.
  • Barley straw extract and peat extract are the active ingredients.
  • Fish and plants may rest easy.

When it comes to eliminating algae naturally, nothing beats a bale of barley straw. Decomposing barley straw is thought to release an anti-algae compound.

TetraPond Barley and Peat Extract provides all the advantages of barley straw without the bother of transporting and dispersing bales. If you’re committed to using only natural algaecides but have a severe infestation, you may need to manually remove a lot of the algae before using this solution.

Instead of destroying algae, Barley and Peat Extract is better at maintaining clear water and avoiding outbreaks. Existing algae can be eradicated with consistent application, but at a considerably slower rate than with chemical algaecides.


  • All-natural
  • Non-toxic to humans, animals, and vegetation
  • Facilitates the maintenance of clean, algae-free pond water.


  • Inching along slowly
  • Defeated by itself when faced with widespread algal growth.

Clarifier for Ponds with Tetra GreenFree UV Light

TetraPond UVC-5 GreenFree UV Clarifiers For Up To 660 Gallons

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  • Types of Algae It Is Effective Against: Green Water Algae
  • The Active Ingredient is UV Light
  • Fish and plants may rest easy.

Our most expensive and unusual algae killer is also the most environmentally friendly and powerful against green water algae.

The GreenFree UV Pond Clarifier needs no professional installation and uses ultraviolet light to effectively eradicate green water algae.

Clearing pond water with this treatment might take up to 8 days. Nonetheless, aquatic life and vegetation are unharmed. The UV Pond Clarifier should be left on after the initial algae bloom has subsided to avoid a resurgence.

This treatment is effective exclusively on green water algae and is hence best suited for use in modest backyard ponds.


  • Uncomplicated to set up
  • Biological control of algae


  • Effective only against green water algae
  • Initial investment is very high.

Factors to Think About Before Making a Purchase

The following are some factors to think about while selecting an algaecide for your pond.

Chemical Algae Killers vs. Natural Algae Killers

How fast you want your algae gone and how comfortable you are with using chemicals in your pond will both go into your decision.

If time is of the essence, a chemical algaecide is the way to go instead of a more natural approach.

Choose a natural algae killer like UV purification or barley straw extract if you’re ready to wait for results in exchange for peace of mind that your pond’s ecology won’t be affected.

How about an oxygen source for your pond?

Even though chemical algaecides are advertised as “fish-safe,” they can still lower pond oxygen levels and kill fish.

The decomposition of dead algae reduces the amount of oxygen in a pond, which can be harmful to the survival of fish and pond vegetation.

Make sure your pond has adequate aeration before you apply a chemical algaecide to it. If you want to err on the side of caution, go with something natural.

Is There a Wall Around Your Pond?

Most chemical algaecides must be used in ponds that are completely isolated from the surrounding environment, meaning no streams or drainage pipes. If your pond doesn’t look like that, then you should use a natural algae treatment.


After reviewing BestForPets (bestforpets.org) reviews of the best pond algaecides & algae killers for ponds, you should start cleaning your pond.

When it comes to eliminating algae overcrowding, API Pond Algaefix  is our top recommendation as it works well for a reasonable price.

Our top recommendation, Tetra Algae Control Pond Block , is a low-cost, long-lasting algaecide that is ideal for home ponds. If you want to keep your fish alive while using an algaecide, be sure to strictly follow all instructions

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Dr. Ramona Terrell

Dr. Terrell has served on the boards of several organizations, including the Wildlife Conservation Society, in addition to her professional affiliations. She is the Veterinarian Director of the Association of Zoos and Aquariums' Exotic Animal Health Program.

Veterinarian (DVM) Dr. Ramona Terrell


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