How to Get Rid Of String Algae | A Practical Guide By Expert


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String algae belong to the genus of green algae. Together with other algae and water lettuce types, they are most often found in pools and aquariums. True to their names, the string type of algae grows in the form of thread or string. They can get to a length of up to 20 cm. This form of filamentous algae (soft and slimy) also develops during the initial phase of an aquarium and makes newcomers especially mad among the aquarium maintainers. The light green and delicate threads of this species float in the current are attached to the decoration. The plants continue to grow from there. In excessive infestation, they form thick cushions, cobwebs, or small clouds of weeds that float around the pond water. Thus, it’s best to learn how to get rid of string algae effectively.

String algae: Its Effects on Aquariums

String algae: Its Effects on Aquariums

The slight growth of string algae in the aquarium can make the tank water values imbalanced. They also introduce high concentrations of pollutants. A carpet of string algae bloom on the water’s surface further serves as a colonization area for many microorganisms, and the oxygen bubbles are also easily captured in it. This results in insufficient food for young fish and degrades the nocturnal supply of oxygen.

String algae are also less welcomed in the display tank. With their green threads, they grow too much on plants, roots, and decorative objects and thus obscure the view of the carefully designed interior and damage infested plants and the sensitive aquarium ecosystem. The algae’s demanding nature in the aquarium also makes them grow where other plants need to hoist the white flag. With this, the water’s nutrient content becomes increasingly unbalanced, and, in the end, the living conditions for the aquarium inhabitants tend to deteriorate.

How to Get Rid Of String Algae: Tools Needed

How to Get Rid Of String Algae: Tools Needed

To get rid of string algae, you will need some tools. This includes:

  • Copper
  • Peroxide
  • Aluminum sulphate  
  • Excavator
  • Ultraviolet sterilizer

How to Get Rid Of String Algae: Steps

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The presence of string algae in a pond or aquarium is often unpleasant for owners. The algae are synonymous with bad odour and cloudy water and do not allow you to enjoy your water in an ideal way. Today, there are diverse ways on how to get rid of string algae or perform algae control. This includes:


When looking for a solution to remove string algae or particularly filamentous algae from your pond, copper is generally the first solution offered. Used in the form of granular copper sulfate, it controls the majority of string and planktonic algae. Thanks to its low cost, it is one of the most widely used solutions to limit algae’s presence in your pond. When used in the form of liquid chelated copper, it controls not only a large part of a string and planktonic algae but also algae attached to the bottom of your pond.

Very efficient and affordable, this solution nevertheless has negative aspects. In the long term, it can bioaccumulate in the sediment present in the pond. Several regulatory bodies single out this phenomenon. Depending on the dosage and the water’s chemical composition, copper is reactive to certain species of fish, such as salmonids.

This danger is less in the case of high hardness and alkaline water. In all, copper is much more effective in removing string algae, but it should be used cautiously. A small percentage (like .2%) is good for your fish, but adding too much will kill your fish and your plants. For example, from a paper we come to end that common plants like water hyacinth and lotus will begin to die back at 0.10%, whereas water lily won’t die off until 0.5%, and to deal with algae effectively, you will want to shoot for 0.25 to 0.30%. (


The peroxides come into contact with the pond algae to eliminate them. The action of peroxides is ultra-fast. Composed of oxygen, it bubbles during its use and is not dangerous for the fish present in the pond, provided that the product is used in compliance with the recommended doses. The peroxide also works to treat algae out of your pond on a roof, outside of a tank, on a ventilator, etc. After use, the remaining filaments and cellulose should be removed from the water; otherwise, they will fall back and collect at the bottom of your pond.

More expensive than other solutions, the use of peroxides to suppress string algae is particularly effective in localized treatments. It is also a suitable solution for small areas such as water gardens. Also, note that it leaves no product residue. Be careful; however: the application rate varies enormously. Remember to consult the instructions on the product label to use it in the best possible conditions.

Aluminum Sulphate  

The aluminium sulfate is used to clean the muddy water or ponds infested with string algae. This solution is not a herbicide but acts just like one. The aluminium sulphate binds the phosphorus, which starves and kills the string algae in the pond.

Despite their effectiveness, chemical solutions are temporary solutions that unfortunately have less effectiveness against string algae in the long term. These processes kill the algae. They then break down in your pond and turn into organic matter. It is this same organic matter that feeds the proliferation of algae. Therefore, using chemical materials has the advantage of quickly removing the algae you see in your pond, but in reality, it amplifies the growth of algae in the long run.


Using ultrasound is a science-based method of removing string algae from your pond. It is the resonance of ultrasonic waves that kills the algae. Here, a transducer submerged underwater generates sound waves that tear apart the gas vacuole, allowing the algae to float, causing their death.

Despite being very expensive, this solution has the drawback of not being effective in all ponds. The device must be adapted to the quality of the water to improve its action against algae. Also, care has to be taken when using ultrasound to kill the string algae in your pond, as new algae can take over and not be impacted by this solution. This stuff can be gotten @ Dollar General, and it’s sometimes a 3% solution.

Pond Cleaning

The cleaning of the pond is an effective method used to remove string algae. It is a solution that consists of using an excavator to get rid of the string algae present in the pond. Very effective, this cleaning removes every string of algae, as well as the nutrients that nourish them.

Learn More: How To Get Rid Of A Small Beehive

Ultraviolet Sterilizer

The ultraviolet sterilizer works using the wavelength of light, which will suppress every string of algae. This solution is also very effective in treating green water but is ineffective against filamentous or erect algae. The ultraviolet sterilizer is further suitable for small ponds and aquariums. But, due to its high price, it is not optimal for large ponds.

Use of bacteria

Using bacteria in your pond to get rid of the string algae is a natural approach based on living organisms’ use. The bacteria feed on the excess nutrients present in the pond and thus starve the string algae. By introducing beneficial bacteria, you are, therefore, contributing to the death of unwanted algae.

Not categorized as herbicides, bacteria do not kill algae. The interest in their use lies in their ability to regulate nutrients. This allows you to control the number of algae present in your pond. When bacteria are present in your pond in the right proportions, they also biodegrade silt, improve water quality and odour, and decrease the number of solids and particles in the water. They also help transform waste from fish into harmless nitrates, so your wildlife won’t die of ammonia poisoning afterwards.

For an optimal result when using bacteria in your pond to get rid of the string algae, we advise you to respect the following prescriptions:

Bacteria are living organisms. The parallel use of herbicide will have the effect of killing them and rendering their effect null.

The dissolved oxygen levels present in the pond should be at least 2ppm

The lower the water temperature, the more the effectiveness of the bacteria present in the pond decreases.

Useful in the long term, using bacteria in your pond is an ideal solution to increase water quality sustainably while respecting your pond.

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Use of Fish

The presence of sterile herbivorous fishes in the pond can effectively regulate the presence of string algae. True to popular belief, sterile herbivorous fishes usually eliminate algae by eating them. The integration of the sterile herbivorous fishes in the pond also makes it possible to change the pond’s fauna. This, in turn, impacts the food chain, which governs the life of this body of water and subsequently reduces the presence of the string algae.

Barley Straw

Barley straw is a natural alternative to the herbicides used to control string algae in ponds. It lowers the PH level and the water’s carbonate hardness, helping the pond keep the right balance. This phenomenon helps control the growth of unwanted plants, such as string algae.  

When barley straw comes in contact with water and light in the pond, it creates peroxide, killing filamentous and string algae. The effectiveness of this technique, unfortunately, varies from one pond to another.

How to Get Rid Of String Algae: FAQ Section

What will eat string algae?

String algae are usually eaten by sterile herbivorous fishes such as Otocinclus Catfish and Twig Catfish.

What naturally kills algae?

Algae can be naturally killed by Barley straw. A shade also works effectively here. First, many will provide shade (looking to cover approximately 50% of a full sun covered pond); shade will help prevent a surge of algae growth, particularly in the high heat of summer. The “magic” number of shooting for aquatic plant coverage is 60-70% surface coverage.

Does hydrogen peroxide kill string algae?

Yes. As earlier highlighted, hydrogen peroxide kills string algae. For this, use a Dose Hydrogen Peroxide (3% peroxide, approx. 16oz per 1,000 gallons).

Does anything eat hair algae?

With the recent increase in hair algae on wild reefs, there has been an upsurge in research into managing and eradicating it. Several fish species have shown themselves to be effective at eating certain types of this pesky nuisance from rocks, including Florida flagfish Jordanella floridae or Ameca splendens, as well as some mollies. However, most shrimp don’t seem interested enough in leisurely swimming around through slimy green stuff for long periods like these other creatures do!

Several fish and invertebrates will eat at least some species of nasty hair algae that is spreading across our natural coral reefs right now–some successful ones are Florida Flagfinning (Jordanella Floridae), America Splendens.

Will UV light kill string algae?

UV light is a form of electromagnetic that can penetrate up to one foot into the water. UV lights do not kill string algae. String algae are attached to different parts of your pond and therefore will not flow past the UV light. Nualgi Ponds eliminates the need for a UV light, and we do not recommend using a UV light while using Nualgi Ponds.


In conclusion, string algae tend to affect ponds and aquariums negatively. And if you desire to learn how to get rid of string algae effectively, the solution has been highlighted above. Furthermore, to reinforce these solutions’ effectiveness, it is also advantageous to take steps to prevent the appearance of string algae upstream.

The aeration of your pond is, for example, a beneficial process, which, by mixing the water, increases the quality of the water by bringing homogeneity to your pond. Small water changes (10-15%) up to once every 1-2 weeks also help renew specific minerals in your pond that deplete with time and prevent the thriving of the string algae.

Read More: How to Lower Nitrogen in Soil

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