How to Remove Algae From a Pond

Algae is a natural part of a healthy pond ecosystem, but when growth starts to get a little out of control, it can quickly become a bit of a problem. Excessive algae can turn clear water green and form dense mats across the surface, which can contribute to poor water quality and fluctuating oxygen levels.

If you want to remove algae from a pond, it is very important that you look beyond just removing what you can see. Physical removal can indeed provide an immediate improvement, but unless you actually look to address the conditions that are allowing excessive algae to thrive, it is highly likely to return.

Understanding exactly what is causing the growth is therefore the first step towards achieving longer lasting control.

What Causes Algae in a Pond?

Algae needs several things in order to grow, including sunlight and water, along with sufficient nutrients. A pond naturally provides these conditions, which is why completely eliminating algae is neither realistic nor a desirable goal.

Problems start to arise when the balance changes and algae has access to an excessive supply of nutrients.

Some of the most common contributing factors include:

• High levels of nitrogen and phosphorus
• Agricultural or fertiliser runoff
• Fish waste
• Decaying leaves and vegetation
• Organic matter accumulating on the pond bed
• Poor circulation of the water in the pond
• Warmer weather and prolonged sunlight
• Low or unstable dissolved oxygen levels

Several of these factors will usually occur at the same time.

For example, organic matter might start to gradually build up on the bottom of a poorly circulated pond. As it decomposes, nutrients can become available within the water, which creates favourable conditions for further algae growth.

This is exactly why just treating the visible algae may only provide you with temporary results.

How Can You Remove Algae From a Pond?

The best approach here will depend on the type and severity of algae that is present and the size of the pond.

For more established ponds, algae management will often involve many different methods rather than relying on just one treatment on its own. 

Physically Remove Excessive Pond Algae

Where algae has started to form floating mats or dense strands, physical removal can provide you with an immediate improvement.

Rakes or nets can be used to remove accessible algae from the water.

Removing the material rather than allowing it to die and decompose within the pond is very important, as decomposition consumes oxygen then releases nutrients back into the water, which can then potentially contribute to another cycle of growth.

Physical removal is therefore very important, but it does not usually address the underlying reason the algae appeared in the first place. 

Improve Pond Circulation and Aeration

Poor circulation can create stagnant areas where water quality deteriorates and algae can flourish.

A pond aerator moves water and increases interaction between the water and oxygen. Depending on the system that is used, this can improve circulation throughout a significant proportion of the waterbody, which helps to maintain healthier dissolved oxygen conditions.

Improved oxygen availability also supports the aerobic microorganisms that are responsible for breaking down organic material.

For larger ponds, a professionally specified pond aeration system can therefore form an important part of a long term algae management strategy.

Heathland Group manufactures pond aerators that are designed around a multitude of factors including pond size, depth, shape and existing water quality conditions. Correct specification is very important because every pond will behave slightly differently and an aeration system needs to be able to provide sufficient circulation for the particular waterbody.

Reduce Any Excess Nutrients That Are Entering the Pond

If nutrients are continuously entering the pond, algae then has a readily available food source.

It is therefore worth spending some time investigating exactly what is happening around the waterbody as well as within it.

Potential sources can include:

• Fertiliser washing into the pond
• Agricultural runoff
• Waste from high fish populations
• Waterfowl
• Grass clippings
• Fallen leaves
• Decaying aquatic vegetation
• Nutrient rich incoming water

Reducing these inputs when possible can make other algae control measures much more effective going forward.

Buffer planting around the pond may also help intercept some nutrients before they are abel to reach the water.

Remove Accumulated Organic Matter

Leaves, fish waste and other organic materials will gradually start to settle onto the pond bed and as time passes this material can create a layer of nutrient rich sediment or sludge.

Its decomposition will also create more of an oxygen demand. In poorly oxygenated areas, decomposition becomes much less efficient and pond conditions can deteriorate even further.

Removing any excessive sludge when it is appropriate and preventing unnecessary organic material from entering the pond can help tackle one of the underlying contributors to persistent algae problems.

Aeration can complement this approach by maintaining oxygenated conditions that will support natural aerobic decomposition.

Should You Use Chemicals to Remove Pond Algae?

Algaecides and other types of treatments can sometimes provide quite rapid control, but they should always be used very carefully and only when suitable for the particular waterbody.

Killing a large quantity of algae quickly does not make the organic material disappear. The dead algae begins to decompose, and that process consumes dissolved oxygen.

In a pond containing fish, a significant reduction in oxygen can create an additional problem.

Chemical treatment also does not necessarily address excessive nutrients, poor circulation or any accumulated organic matter. If those conditions remain unchanged, algae may simply return.

For persistent problems, identifying and then addressing the underlying environmental conditions will generally provide you with a better foundation for long term management.

Do Pond Aerators Help To Control Algae?

Pond aerators can play an important role in improving the conditions associated with excessive algae, although aeration should not be considered a direct treatment that simply kills algae.

Aeration can increase water movement and improve dissolved oxygen conditions, while reducing stagnant areas.

This can support a healthier pond ecosystem and can improve the biological processes that is involved in breaking down organic material.

The type of aeration system matters.

Surface aerators primarily move and oxygenate water near the surface, while diffused aeration systems release air from diffusers positioned on the pond bed. The rising bubbles encourage water movement through the water column, helping circulate deeper water towards the surface.

The appropriate solution will depend on factors such as pond depth, shape, volume and the particular water quality problems present.

How Long Does It Take to Clear Algae From a Pond?

There is no universal timeframe here, as physical removal can improve the appearance of a pond immediately. While improvements that result from changes to nutrient management and overall pond health can take considerably longer.

Weather also matters here, as warmer temperatures and strong sunlight can encourage rapid algae growth, which means that a pond may behave very differently throughout the year.

The objective should not necessarily be to create perfectly clear water as quickly as possible. Instead, focus on establishing conditions that make excessive algae growth less likely to repeatedly return.

How Can You Prevent Pond Algae From Coming Back?

Prevention involves managing the pond as an ecosystem rather than repeatedly reacting to visible algae.

A longer term management plan may include controlling external nutrient inputs and removing excessive organic debris, while looking to maintain appropriate vegetation and ensure there is adequate circulation and oxygenation.

For ponds that regularly experience stagnant conditions or poor dissolved oxygen levels, a correctly sized pond aerator may provide an effective long term addition to this strategy.

Heathland Group designs and manufactures pond aeration systems in house, allowing systems to be specified according to the characteristics and requirements of individual waterbodies.

Frequently Asked Questions

What is the best way to remove algae from a pond?

There is no one size fits all method that is suitable for every pond. Physical removal can deal with existing algae, while longer term control usually requires identifying contributing factors such as excess nutrients and poor circulation. A combination of approaches is often what is required.

Will a pond aerator get rid of algae?

A pond aerator does not simply kill algae. Aeration can improve circulation and dissolved oxygen conditions, which then helps to create a much healthier aquatic environment and addresses some of the conditions associated with excessive algae growth.

Why does algae keep coming back in my pond?

Recurring algae usually indicates that favourable growing conditions remain within the pond. Excess nutrients, sunlight, warm water, organic matter and poor circulation can all contribute. Removing visible algae without addressing these factors is likely to result in repeated growth.

Is algae harmful to fish?

Small amounts of algae are a normal part of aquatic ecosystems. Excessive algae growth, however, can contribute to significant fluctuations in dissolved oxygen. Large amounts of algae dying and decomposing can also consume oxygen, potentially creating stressful or dangerous conditions for fish.

Does pond aeration improve water quality?

Aeration can improve circulation and dissolved oxygen conditions while supporting aerobic biological processes within the pond. It can therefore form an important part of wider pond water quality management.

Should I completely remove all algae from my pond?

No. Algae occurs naturally and plays a role within aquatic ecosystems. The objective is usually to control excessive growth and address the conditions causing an imbalance rather than attempting to create a completely algae free pond.

Can I prevent algae naturally?

Reducing nutrient inputs, removing excess organic matter, managing vegetation and improving water circulation can all help manage the conditions that encourage excessive algae growth without relying solely on chemical treatments.

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